So, I was very excited about this premise, as it sounded wonderful. Unfortunately, book 1 is so slow it's a slog. We read about the life of a slave for over half of book 1 before he decides to escape. This needed to happen faster. The MC meets some hunters who just happen to know how to get around the slave band that prevents cultivating. Some training happens, he gets to literally the first level of the weakest cultivation level, and then decides he's now strong enough to rescue his sister who is multiple realms in power above him. Huh?
They get into the fort just as the beast wave happens, and bam! The book is over.
What?????
I read a few chapters into book 2, and it does not get better from there. At one point, the MC is supposed to be blending in and lying low, when he sees another refugee that is stronger than him having difficulty with a guard. The guard isn't abusing his power or being unreasonable, kids go to safety below, refugees get resources and help defend the walls. The mother was being dumb and wanting their kid to stay with them on the wall. Our MC decides this is the perfect time to intercede and fights the guard. Why would he risk being thrown in the dungeon and ruin his chances of saving his sister when he has no chance of helping the dumb refugee mother? Who know, but plot armor saves the MC again.
Bottom line, if you like dumb MCs who constantly screw up, but end up winning in the end because of plot armor, this is the series and author for you. This is the 2nd series I have read from this author, and Robyn consistently has this flaw.
At this point, it is just lazy writing.