In case anyone is searching and finds this:
Any weapon with tenebrium on it no longer receives bonuses for the original weapon skill (bow/2hander etc) but receives only the tenebrium weapon skill bonus.
So if you have Tenebrium 1 and Bow 3 on a 100 damage Bow... a bow with tenebrium on deals 110 damage, but a non-tenebrium bow would deal 130.
So don't raise your other weapon skills, just wait for Tenebrium to become unlocked!
