I'm not a fan, personally - I feel there should be a clean possibility for the character to get her out that isn't dependant on specific class choices; the tadpole exists as an option if you struggle and fail; then it's a temptation in the truest sense, because you've tried and failed to do something that you clearly have signalled to the game that you want to do... and *then* the tadpole is there to say "Well, you could do that thing, if you really want to... just let me in a bit, and you can, guaranteed."
If using the tadpole is the only actual way to do the thing that you want to do, then you aren't making a choice to use the tadpole - your choice was the thing you wanted to do, and the tadpole is then the forced only way to do it, and that's going to leave a dissatisfying taste for some people, and others won't be tempted at all. This may seem like splitting hairs to some, but it's an important distinction that has RP weight and impact. I would much prefer my temptations to darkness be made in moments of weakness or failure, when I want or need something that I've personally failed to manage... and I give in, and take the easy way to get there, because I want it, and I couldn't manage it on my own. That's true temptation.
I'd also venture if you do it that way, then it will actually reduce a certain amount of save-scumming for desired outcomes, because more people will be inclined, when they fail, to take that step when it's offered, rather than reloading multiple times. It enhances immersion and roleplay and helps to keep people in the space.
For example:
Everyone, regardless of class, should be able to try to pry the pod open, and should have a chance of succeeding - albeit a hard, but not unbeatable DC; a 17-18 would be fair, for a level 1 character. Everyone can try this... upon failing this a barbarian can get a second try, with the option to expend a rage and take the check again with advantage. this way everyone can try, but the class with a specific ability to give them advantage in this situation has the option to use it and has that edge.
Everyone, regardless of class, should be able to try to disrupt the runic warding that kept the pod shut, and should have a chance of succeeding, again - difficult but not completely unbeatable. Class or race abilities that give you an edge here should be able to come into play for those classes.
Everyone should have a pretty good chance of failing these attempts; they should be hard checks for a level 1 character to make... and the tadpole provides the guarantee, that you can be tempted by when you fail to do what you really want.
This is all nice and good in theory but in practice... people savescum. If you give people an option that can be guaranteed after a load or two, they will do it.
And so(nearly) no one would use the tadpole to free her and it would once again fail to tempt you to use the tadpole. Some options being open to you only if you utilize your newfound power is completely fine, and only when doing so results in the ''good'' outcome, will people generally be tempted by it in the first place.
