it goes like this...make an item for each ability and give it to a store such as the goblin merchant...for this trigger i used the ability immolition and the item as a perpiate of vitality...
- - - - - - - - - - - - - - - - - - - -
Ability 1
Events
Unit - A unit Sells an item (from shop)
Conditions
(Item-type of (Sold Item)) Equal to Periapt of Vitality
Actions
Hero - Learn skill for (Triggering unit): Immolation
Item - Remove (Sold Item)