BTW, the normal weapon skills seem to work as well above level 5,just noticed when I reached two-handed 5 that there is an option for level 6 too.
All weapon skills will give you a 10% bonus per level in that ability. The big difference for Tenebrium weapons is that you will have a passive +2 Bonus (1 from Brandon's Quest and 1 from the Geomancer's book), which means you can get to level 10 in that ability (+3 from rings and amulets) for a 100% damage bonus.
