Webnovel.Forum

I was reading a novel a while ago and thought of reading it again but I can't remember it's name.
It's like a tower of god setting where they have to survive and gain skills.the mc reincarnated to the beginning or something and uses his memory to get better skills. Like he climbed a mountain or something and got a necromanct skill. I remember parts of it. One part of it was about the mc climbing a tower and the had to kill 5 people to get out. The 2nd starts slaughtering everyone and he kills a group of people and they turn into a group of zombies called Prince and his something in the end he kills like 396 people and gets the title of slayer or something. There is another part in the beginning where he goes to a library and they have a chance to get a skill book and he gets the best one called the of something
Sorry it's a bad description
Thanks in advance