For some mutations a skill roll will be required to activate them. Thus the skill will be directly used. For most mutations that contain some kind of variable (e.g. the amount of protection they provide, the range at which they work, the damage they might cause) the mutation skill modifier will be used in order to find the level of effect for the mutation based on a universal quantifier table (UQT).
The universal quantifier table takes a dimension (e.g. damage, distance, weight or area) and maps an abstract score to a specific value. E.g. the description of the "laser eye beam" mutation might indicate, that the character can shoot laser beams from his eyes at a range of (4 + MSM), causing (2 + MSM) damage.
MSM here stands for "mutational skill modifier". The two abstract values are mapped to specific dimensions (for an example character with "Mutation Skill: Layer Eye Beams" of 16, garnering an MSM of +2):
- The abstract range value of (4 + MSM) equals 6, which might be mapped to a specific range of 50 yards.
- The abstract damage value of (2 + MSM) equals 4, which might be mapped to 4d6 actual damage.
As a side effect I BTW have created a new Mutation skill area for Gaia Gamma, which mutated humans receive for free at rank 1 and sentient plants and altered animals gain for free at rank 2 (see this older post for explanations about skill area ranks).
There is one feeling of doubt left with me, though. Is this too much for an old school game and am I introducing too much modern stuff into the game? Let me know your thoughts and help me to shape the game!