It's a shame the wiki is all over the place concerning CoC.
There are two types of tentacle cocks in the game, plant and anenome ones.
Anemone cocks: by "giving birth" to one after the anemone female fuck scene.
Plant tentacles: by checking the corrupted glades vines. If your Champion's hair is already green and has at least one non-tentacle penis, there is a 1/3 chance all of them will become tentacles.
So You can supposedly get multiple with incubus draft, normal or purified, but I can't seem to get it to happen. That's if the wiki on it is still accurate.
Well corruption is 100 and libido is at 46. Honestly Libido is probably the hardest thing to control in the game. I had a time getting enough to corrupt Jojo.