Hi,
so one of my players wants to use the 2nd level spell "Alter Self" to assume the form of a Sewer Troll that has 10 ft reach with its two natural claw attacks and additional perks like scent, darkvision, and lowlight vision.
To be honest I do not feel comfortable to allow a character to just assume any humanoid form just because the player has checked every humanoid race to identify the races with the best mechanic benefits.
So I am asking for knowledge(local) checks. The DC is clear with CR of the creature + 10 (or 5 or 15 depending on how common the race is).
RAW it sais "For every 5 points by which your check result exceeds the DC, you recall another piece of useful information."
So if the player wants a certain common CR1 race because of it swim speed and darkvision, could I ask for a DC 21 (10 base + 1 for CR + 5 for swim + 5 for darkvision) so that the character knows about this race?
This methodology can be applied to other polymorph spells although it gets more and more difficult when the CR increases.
What do you think of this methodology? Do you use another methodology or can you think of another way?
Thanks a lot!