As for necromancers, they're at least theoretically in control during the whole process if they became a Lich. With the tadpole, you have no control over it
How so?
Its you who are reaching for their power ... its you who are using them ... yes it may affect/corupt you in return, just as necrotic magic does.
no understanding of how it works
Thats also not necesarily true ...
Our characzer can be educated enough to know regular ceremorphosis, just as Gale or Lae'zel are.
Or you ca be ignorant to the process as Astarion, Karlach or Wyll are.
and you do know that using it immediately costs you something whether you like it or not. Usi.
Maybe i remember something wrong ...
But isnt this said after some time? I believe first few uses seemed consequence free.
But even if not you find out only after ... it dont come with sign "warning coruptable powers are bad for your mental health".
Also "loose something" is quite vague description ...
When you loose your virginity is that purely bad?
(I gues it depends on who you ask
)
