My first two playthroughs I did not use the tadpoles. I didn't want the physical change and I wanted to make sure I could beat the game without becoming illithid.
In my current playthrough, I used the Astral Tadpole. The difference is night and day. The skills are actually EXTREMELY FUN to use. It feels like you shifted from playing a mortal character, to God-Mode. It's very satisfying continuously flying from rooftop to rooftop.
Illithids can just use fly as an action, it's not like using Fly with a wizard who can only cast it for 10 turns.
There are two Illithid skills in particular, that are absolutely OP
One is called Mind Sanctuary - Creates a dome, where all characters standing underneath can use bonus actions as actions.
The second ability is called Free Cast. Free Cast allows you to use spells, WITHOUT EXPENDING A SPELL SLOT
It's basically the same skills you would normally would use, but enhanced. Your Melee characters can use bonus actions to attack; your spell casters can use bonus actions to attack AND their spell slot won't even go down when they use them. You only need one character to become part-illithid and the other characters can all take advantage of the mind sanctuary.
I expected there to be some sort of consequence to using the tadpoles, but aside from the cosmetic changes, there really weren't any. Feels like they're rewarding you for taking advantage of the extra skills rather than punishing you for it.
