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.
True, but a wizard is able to study necromancy, to understand how it works and why it does what it does, what risks there are, etc, things you can't do with the tadpole. To provide a visceral example, imagine invoking tadpole powers is like reaching into a box of invisible knives. You might come out unscathed, but if you do it's by pure luck. Necromancy is like reaching into that same box of knives but fully lit. You're still likely to get cut, but you can at least do things to mitigate the damage, or at the very least understand how much damage is at stake.
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.[/quote]
They know how normal ceremorphosis works, but not whatever bizarre aberration they're experiencing now.All they know is that it's not working the way it should and they have some unknown amount of time longer than they normally would. So knoweldge of regular ceremorphosis doesn't really help that much.
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".

[/quote]
I'll admit that I can't exactly remember when the warning comes up either.
Also "loose something" is quite vague description ...
When you loose your virginity is that purely bad?
(I gues it depends on who you ask

)
But you don't actually know what you're losing. And if you want to make a guess then well, you're dealing with creatures that eat and mess with mortal brains, and invoking power from a creature that's firmly in your brain. The first assumption most anyone would make is that you're losing something relating to your brain/mind. And even if you don't make that assumption, losing something that you don't know about, it could be unimportant sure, but it could also be very important.