So I got to general today, and I thought I'd share some info about abyss abilities, since i haven't seen much reliable info.
Apparently you get abyss transformation at 5-star, but you only get one ability with that transformation. You get a new ability every rank higher from 5-star up. Also your abilities level up too. You can only use abyss abilities in your transformed state.
To transform you need to buy these. They are 500 abyss points each. At 5-star you need 6 which will cost you 3000 abyss points. Each rank higher than 5-star you need 1 more extra to transform. Therefore I need 7 since I am general rank which will cost 3500 abyss points.
Well here are the 2 abyss skills I have and the transformation skill so you guys can see what exactly it does.
When you get to CnC you get a total of 4 skills + the transformation skill. Honestly, the transformation is strong, but you still will drop super fast if you don't have clerics healing you constantly. You probably at most could take on a group by yourself. All in all it's not that worth it lol. But anways, I am trying to get to CnC and I am still doing some testings. I will keep you guys updated with new info.