So, what is your ruling on how much alteration Physical Mask does? Can it change retinal prints? In either case, Arachnos is going to cast Physical Mask to, well, mask his features. His paranoia got the better of him.
Casting Physical Mask at Force 4 [Spellcasting 6 + Magic 6 + Mentor Spirit 2 + Illusion Focus 4]:
18d6t5 4 [2, 4, 5, 3, 3, 1, 4, 4, 1, 2, 2, 5, 2, 1, 5, 2, 3, 6]
Perfect, just hit the limit. Now, to resist Drain.
Resisting 3S Drain (Charisma 6 + Willpower 5):
11d6t5 2 [1, 4, 2, 6, 1, 3, 1, 4, 5, 4, 3]
Well; 1S drain for me.
Now, for anyone to pierce that disguise, they need to beat a threshold of 4. Living beings resist with Intuition + Logic; technological devices resist with their Object Resistance.