Spider mutation gives a pair of extra eyes.
Actually they don't really work so they don't give bonus but just makes the Kise more... disturbing?
This mutation have a few interactions with markings and other mutations:
WIP
If the Kise was born blind, every eye must be shown as so.
If the mutation was acquired, you're free to blind only one eye.
WIP
If Crystal eyes mutation is present, both eyes must be of the same colour.
Shade might be slightly different, but shouldn't be extreme (dark green vs lime green would be a no-no!)