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Monster Security Agency #13

Guarded by the Symbiote: Monster Security Agency

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The second she lets me in, I’m a ruined man.

I’ve been merging with hosts my entire life. Slipping under their skin, living in their minds, protecting them – it’s what I do. I’m a professional, and I keep my distance.

Then I’m hired to be her bodyguard.

An undercover cop infiltrating the deadliest criminal organization in the country, and I’m her hidden weapon. Merged with her body, experiencing her every thought, her every desire. I’m supposed to protect her and stay detached.

But her thoughts unravel me. The fantasies she’s been hiding drive me insane. She wants to surrender, to be claimed by someone strong enough to handle her intensity. And I’m a monster too dangerous for anyone to want.

I become addicted and terrified, knowing that when I must separate from her, I'll leave my sanity behind.

304 pages, Kindle Edition

Published December 22, 2025

49 people are currently reading
60 people want to read

About the author

Cara Wylde

147 books649 followers
Cara Wylde loves to write about strong, feisty women and their hot Alphas who will do anything to make them happy. Her books are filled with romance and just a dash of mystery, suspense, and that eerie atmosphere she fell in love with reading too many gothic novels. With a master's degree in Comparative Literature, she can't help but play with tropes and themes from various genres, trying to come up with fresh perspectives on the paranormal characters her readers love so much. Vampires, shape-shifters, demons, witches... Cara will always make sure they get their own twists.

When she's not writing, Cara is reading, planning her next story, or daydreaming. Her idea of pure heaven is a day filled with nothing but her laptop, a huge coffee pot, relaxing music, and a new, exciting project.

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5 stars
113 (52%)
4 stars
58 (26%)
3 stars
35 (16%)
2 stars
9 (4%)
1 star
1 (<1%)
Displaying 1 - 30 of 44 reviews
Profile Image for adriana.
399 reviews10 followers
December 29, 2025
I’m on a dnf’ing spree it seems, but, that doesn’t take away from the fact that this was over the top CRINGE. 🙄🫩

Every scene I read of the mcs together played out so damn awkwardly in my head.

From what I gather, this FBI agent’s big dirty secret that she can’t keep under raps FOR EVEN A MINUTE AROUND HIM is that she’s a horny monster lover? And her horniness is so strong that it overrides every ounce of professionalism in her?? So horny, that getting up from laying down causes her pants’ seam to overstimulate her clit???

Give me a break! 🤦🏻‍♀️

I also have to mention how the fmc acted like such an asshole… First she made an ignorant, prejudice comment towards the mmc regarding his species, & then she refused to shake hands with him.
This entire review has been hidden because of spoilers.
Profile Image for Andi Downs.
1,459 reviews14 followers
January 11, 2026
Fantastic series and such great authors with great characters created for us to enjoy. Always happy to read any new books in this series.
I received a free copy of this book via Booksprout and am voluntarily leaving a review.
Profile Image for SheMyaReads.
149 reviews1 follower
January 6, 2026
🤩

I enjoyed this book so much it reminded me of venom and it was amazing. Rhea and Zeth are so cute together and balance each other out. And my poor Zeth his backstory had me in almost tears.
Profile Image for Laura Moylan.
1,519 reviews
December 27, 2025
Wren is staying at a dump of a motel and is looking for work. She is a chemist, and she is kidnapped, and finds herself in a warehouse, with a man, a golem, and some sort of undead. Since she has just gotten out of prison and is in need of work, they figure to test her and her skills in making an illegal drug. We find out that a few weeks earlier, Wren was called into Captain David Holt’s office to be put into the Kyzers drug ring, since they arrested the chemist that worked for them. As an FBI agent, she will go in under cover, but they want to give her a symbiote as her bodyguard. They will link, and he will be there to help her and protect her while undercover. Since the Kyzer’s chemist has been gone for two weeks, the production of Crimson Haze has stopped. Since it is made from basilisk venom and vampire blood, there aren’t many that can make a batch that isn’t useless or lethal. She doesn’t want the bodyguard because she has secrets. I found the information of what a symbiote can do to be fascinating. The story was enthralling, and I couldn’t put the book down. Forced to accept that she needed the symbiote bodyguard or it was a no go for the op, she does it. Zeth Thessian is his name. Zeth is instantly fascinated by Wren. They practice merging and after a few times, they are good to go, just in time.

Wren is upset that while they are merged she is feeling things that she doesn’t understand. Zeth begins to understand why and explains a bit to her. They are uncomfortable with each other at first and then things kind of work out well just in time. She passes the test and shows that her Crimson Haze is actually better than the previous chemist’s. She is pretty much in a lockdown and expected to make vast amounts of product. How Zeth & Wren handle things weren’t what I expected, but was oh so good. I was impressed.

The book is fun, sweet, romantic, steamy, weird, scary, enthralling and I chewed on my nails and cried a few times.

There are a few times where something happens and it is all Wren can do to calm Zeth down from doing something stupid, because he wants to protect her and he is possessive of her. The youngest son of Viktor Kyzer, the kingpin, Roman, is in charge of her. He does something I never thought and it gets crazy and scary from there on out and I needed the AC on high, from freaking out. Wren shows that she can turn Crimson Haze into something even more unique with another ingredient, and that impresses the kingpin. Wren’s circumstances change after that and then things get weirder. But, the majority is all for the good for the FBI. lol. My nerves were shot for this section of the book. We find out more of Zeth’s past and I cried for him. We find out Wren’s true name and Zeth talks to her after their debriefing. I love the ending. I can’t wait to see what happens next in this world.

I received a free copy of this book via Booksprout and am voluntarily leaving a review.
Profile Image for Vanessa.
131 reviews1 follower
December 28, 2025
This book got under my skin

I was intrigued by the premise of this book, and I loved how the merging of the two main characters illustrated both the fears and deepening of what it means to be intimate with another. Here we have an undercover FBI agent—already living a false identity, already surveilled in every room except the bathroom—who must merge with a symbiote that will know her every thought. It’s the ultimate threshold: what happens when hiding becomes impossible?

What unfolds is a profound exploration of consent through transparency. The symbiote sees everything—even her discomfort about needing to pee while he’s merged with her at the molecular level—yet maintains her sovereignty through radical respect. This isn’t the surveillance state’s cold watching; it’s witnessing with love. He can walk in her shoes because he literally sees through her eyes, yet their consciousness remains beautifully separate.

I also enjoyed how they interact in her dreams, where he consciously chooses whether to participate, showing that intimacy is just as real in non-physical realms. Their sexual encounters in the dreamscape raise fascinating questions about where consciousness truly lives and how we connect beyond our bodies.

This book offers a model for what we actually crave: not privacy from surveillance, but the safety of being truly seen and accepted without judgment. It shows that being molecularly known by another—this ultimate “monster” who gets under your skin—can create more freedom, not less. This is a partnership that illustrates how real safety creates surrender, while surveillance only creates performance.
Profile Image for Mishka.
118 reviews2 followers
December 29, 2025
⭐⭐⭐⭐⭐ UNHINGED. FIVE STARS.

I inhaled this book.

I knew it was going to be five stars before I even opened it. The second I saw Guarded by the Symbiote was coming out, I was waiting. Not hoping. Waiting with expectation. The dangerous kind.
I started reading with my heart already racing. That almost never ends well. Most books fold under that pressure.

This one didn’t.

From the opening, my body was locked in. Pulse up. Focus narrowed. That keyed-in feeling where you’re not just reading, you’re braced. I don’t care about pacing charts or structure when a book does that to me. My nervous system made the call.

The energy was instantly familiar to me. The same way Guarded by the Snake by Layla Fae hit me. Not because the stories are the same, but because the effect is. That deep, visceral sense of being claimed, watched, protected in a way that isn’t gentle and doesn’t apologize for itself.

I trust this genre. I know how it works. And this book understood exactly what it was doing.

No over-explaining.
No sanding down the edges.
No moral safety rails.

Just intensity, inevitability, and that feral protector bond that sinks into your chest and stays there.
I was excited going in. I was feral coming out.

Five stars. Not a recommendation.
An inevitability
Profile Image for Carole.
2,051 reviews15 followers
December 26, 2025
Guarded by the Symbiote is an entertaining addition to the Monster Security series both an imaginative and a deliciously engaging story.
MFC Wren Hayes is being sent deep under cover into a criminal organization and is forced to accept a bodyguards protection, a symbiote who some call parasites a derogatory term she tries to avoid but the thought of merging herself with another being is daunting and chills her, but the mission is too important to abandon.
MMC Zeth Thessian has never worked or merged with a female before which was his only discomforting thought when accepting his new assignment.
Danger, personal vulnerability, intrigue, suspense, passion and good writing keeps the story flowing at a nice pace as the emotions begin to creep into their partnership becoming something they never would have anticipated happening.
I found this a very enjoyable monster romance as events played out and discovered one captivating read!.

I received a free copy of this book via Booksprout and am voluntarily leaving a review.
91 reviews
December 27, 2025
Guarded by the Symbiote by Cara Wylde was such a solid paranormal monster romance. I was pulled in right away by the undercover setup—Wren is a total badass agent going deep into a dangerous criminal organization, and the tension never lets up.

Zeth, the symbiote assigned to protect her, was everything I wanted in a protective monster hero. Their relationship builds in such a satisfying way. Watching Wren slowly learn to trust him—and seeing Zeth open up despite everything he’s been through—was honestly one of the most fulfilling parts of the story.

Both characters carry a lot of trauma, and I loved how that was handled. Their growth felt earned, not rushed, and their connection developed naturally as they leaned on each other to survive both the mission and their pasts.

If you love paranormal monster romance with action, emotional depth, and a relationship that actually grows on the page, this one is absolutely worth the read.

I received a free copy of this book via Booksprout and am voluntarily leaving a review.
Profile Image for Sydnee Walsh.
1,279 reviews30 followers
Review of advance copy received from Author
December 21, 2025
Rhea is a fun character. She is a strong independent agent. So when she is told she needs a bodyguard she isn’t happy. But when it’s a Symbiote that is not anything she wants to deal with at all. They are known as a parasitic species. But for Zeth he has a different reaction. He isn’t a parasite he is a person. He hasn’t gotten over how people react to him because of what he is. He has a big heart and it’s hard for him to understand how people treat his kind.
His childhood has shown him the horrors that people do to his people. He has come a long way to actually work as an agent for Monsters Security Agency.
Their connection and the level of attraction is so hot. It leaves you to want them to stay together. They have a job to complete that is extremely dangerous but at the same time being one makes them see things clearly fast.
516 reviews8 followers
January 2, 2026

Guarding From Within

What I enjoy most about this series is the variety of creatures utilized in the Monster Security Agency. Zeth has the capability of incorporating himself into a human without being visible and that person now has his strength if needed for protection. It’s a relationship of symbiosis, mutually beneficial. Working undercover in the FBI, Rhea is tasked with infiltrating a drug cartel. Zeth is called in as her bodyguard.
Read about this odd relationship and how eventually Rhea becomes acclimated to his necessary intrusion into her physically and mentally. The author deserves credit for reliably conveying the MFC’s wariness and mistrust through internal dialogues between herself and Zeth. This is a very fascinating read and worth 4 stars 🌟.
I have received an ARC from Booksprout and I am leaving an unbiased review voluntarily.
Profile Image for Becky.
1,698 reviews4 followers
December 30, 2025
I don't know where to begin with this review. First, I love all the Monster Security Agency books, and this one is a fantastic addition. Wren is an FBI agent working undercover, and Zeth is hired as her bodyguard. He is an excellent hire because he can merge with Wren, and no one knows he's there. This book has some great twists and kept me on the edge of my seat until the end. I love how Zeth and Wren built a relationship and trust. This book is so good that I will be saving it in my reread file! There is a lot of spice and the very best happy ending.

I received a free copy of this book via Booksprout and am voluntarily leaving a review.
467 reviews
January 2, 2026
Set within the Monster Security Agency series, Guarded by the Symbiote is a paranormal romance with sci-fi elements that instantly drag you into this tale. First thing I think of is Venom, the Symbiote who crawled under Eddie’s skin, but this tale is between a female cop and the one sent to guard her while undercover. Not so keen on the idea, until it’s presented as an ultimatum, she begrudgingly accepts. It’s a quick read that sucks you in until the conclusion. Plenty of danger and action to add to the budding romance.

I received a free copy of this book via Booksprout and am voluntarily leaving a review.
Profile Image for Daria.
1,999 reviews42 followers
December 23, 2025
Inside looking out

Ive loved this series so much. The newest addition fits right on in. A fun read. As monsters go this is one i hadn't thought of. Very unique. What best way to guard a body, then to get up close and personal. Z can put a whole new meaning to that term.
She's tough and single minded. She's undercover in a dangerous situation. The requires a body guard of Zeths capabilities. When they first meet, it doesn't go well. Mostly her fault.
Well things get sticky and feels start feeling.
Very cool story and loved the characters.
18 reviews1 follower
December 31, 2025
⭐️⭐️Must Read⭐️⭐️

This is the first book from this author that I enjoyed. I’ve been delving into the MSA and this book didn’t disappoint. This whole book was perfectly written and I devoured it. I normally find myself either skimming her books because of too much inner monologue or not finishing because of failed plots- in my opinion. But let me tell you, this book kicked some serious hiney.
Great character development along with the story line and amazing HEA. A must read for sure!
Profile Image for Mystisith.
697 reviews10 followers
January 2, 2026
Premise was interesting but execution was disappointing. The lightning in a bottle that was the Snake story in this series seems hard to replicate (yes, the wink & nudges were spotted). I especially didn't like the lasting reluctance of the heroine. Like girl, if you are a wimp & are not interested many of us would treat the guy right & would know how to lead this relationship. Also, you'd think that as an agent, HIS trauma would be known & would have been handled by a therapist... 🙄
The undercover side of the story felt flat & performative.
The spice was meh too.

This entire review has been hidden because of spoilers.
Profile Image for Alex Silver.
626 reviews24 followers
January 3, 2026
2/5

If she weren’t so rude and resistant I may have enjoyed it more. As it was, she was a bitch who called him a slur when she first was told about him and refused to shake his hand when they first met. His attraction to her made no sense. Also, the writing was pretty mid.


Monster (symbiote with a humanoid form). Bodyguard. Undercover cop FMC. Huge cock. Sexy dreams. She is resistant. Squirting. Sex during dreams. He saves her. Epilogue with them as partners in the FBI and dating.

Trigger warnings: he was sexually abused in the past. Violence. Murder. Kidnapping. Drug use.
This entire review has been hidden because of spoilers.
Profile Image for Michelle.
10.7k reviews28 followers
January 6, 2026
Wren, an FBI agent, is being sent deep undercover, and Zeth is the symbiote assigned to protect her. This is an action packed, paranormal, monster romance with intriguing characters, danger, suspense, steam, and unexpected twists that made this a page turner. This is a captivating, well written story and a great addition to the multi-author Monster Security Agency series. I recommend this book, this series, and this author to everyone who loves reading monster romances. I voluntarily reviewed a copy of this book.
Profile Image for Lisa Bing.
6,237 reviews70 followers
December 25, 2025
This is another fun and unique monster romance and a fab addition to the series. Wren needs a bodyguard to go undercover and Zeth is assigned to her. He can infiltrate her mind and I love how practical he was. He didn't judge her for her thoughts...although they intrigued him ;) Expect to get caught up in the action, drama, danger, emotions, suspense and hot romance when you dive into this page turner. So good and I can't wait for more books like this :D
Profile Image for Johanna.
1,511 reviews38 followers
December 28, 2025
This is part of the Monster Security Agency series. Can be read as a standalone.

The characters were very complex and complicated and compelling and perfect together. Plot was intriguing and exciting and well paced. World building was excellent and impressive. Thoroughly enjoyed and highly recommend.

Grab a copy, kick back and enjoy!.

I received a free copy of this book via Booksprout and am voluntarily leaving a review.
Profile Image for Lizzy Love ❤.
182 reviews1 follower
January 7, 2026
I have read this entire series and every single one i feel different about this one though i would definitely put in my top five of the series. i loved the characters, the trauma, the fact he needed full consent from her and willing to wait was swoon worthy. i almost cried at several parts, i loved the little things that happened and the cherry on top with the double epilogue was a nice touch. i gave it 4 stars and the spice was spicing the lucid dreams and the "breakfast in bed" 🥵😏
Profile Image for Angela.
3,547 reviews16 followers
Review of advance copy
December 21, 2025
I enjoyed this monster story. Wren's hesitation to have Zeth's presence in both her investigation into the drug trade as well as inside her body is understandable. Trust is hard to gain, especially in intense situations. His patience with her aversion and his practicality in other aspects proved he was a valuable addition.
Profile Image for NekomataGami.
22 reviews
December 24, 2025
I NEED MORE BOOKS LIKE THIS PLZ

I really enjoyed this book, because I've been looking so long and hard on the internet for this kind of romance.

Not the one romance I had in mind tbh, but this book comes VERY CLOSE.

AND I LOVED IT.

My only complaint is that God's name in vain was used in this book a whole bunch.
Profile Image for Trixie.
5,201 reviews
December 28, 2025
This is such a fun read! Just imagine merging with someone you're seriously attracted to—how awkward yet kind of amazing that can be! It’s impressive how they pulled off their mission. In the end, their partnership turned out to be exactly what they needed.

I received a free copy of this book via Booksprout and am voluntarily leaving a review.
422 reviews12 followers
December 27, 2025
I loved this weird book. It has the most
Interesting MMC and FMC with secrets and smarts. This story was fascinating especially with what his species can do. And the whole chemist aspect was awesome. It gets dicey but they come out in the end. I love this whole series and each one is so different!!!!
409 reviews3 followers
December 28, 2025
Wren has to go undercover to capture a crime ring, but this she has a very special bodyguard recruited from the MSA. Zeth is a symbiote and protects Wren very closely. Tons of tension with heat, yearning, and spicy romance! Loved it!!!.

I received a free copy of this book via Booksprout and am voluntarily leaving a review.
3,273 reviews20 followers
December 30, 2025

Intimate and Action-packed
In order to complete her op, Wren has to merge with Zeth, a symbiote. There’s dangers aplenty, but what worries Wren the most is the lack of privacy and alone time. I loved how these two struggled to mesh, but then it worked out, whoowee those red hot dreams were delicious. An action packed read.
143 reviews3 followers
January 3, 2026
Creative!

I really loved this story because of the vulnerability of both characters trying to come together for the mission given. Both with their own issues. Both wanting each other so badly. I loved how the story grew both characters closer and allowed them to be there for each other. A new fav!
24 reviews
Review of advance copy
December 18, 2025
This was such a good book. The spice was spicy and their chemistry was great. Highly recommend! Great addition to the series.

I received a free copy of this book via Booksprout and am voluntarily leaving a review.
8,829 reviews63 followers
December 21, 2025
Wren is going undercover on a dangerous mission and is given a Symbiote in Zeth to protect her, blending her mind with his, he learns all her dark desires, ones he wants to fufil. Well written steamy, spicy, protection, fast read.
Displaying 1 - 30 of 44 reviews

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