Scales

Level 1
Natural Def I: -1 to all physical rolls to do

Level 2
Cost: 20 XP

Natural Def II: -2 to all physical rolls to do

Level 3
Cost: 40 XP

Natural Def Bonus I: -1 to all physical rolls to do

OR

[Insert Type] Scales I: Whenever someone in combat touches your scales, they take 1 (Poison, Fire, Holy, Unholy, Ice) Dmg.

Lv.4 60 XP

Natural Def III: -3 to all physical rolls

Level 5
Cost: 80 XP

The abilty you picked from level 3 gets leveled up to level II..