Ability.
Claws of attack's ability (item hero damage increase or something like that). No icon visible.
Trigger
Events
Unit - A unit Gains a level
Conditions
(Unit-type of (Leveling Hero)) Equal to YourUnit
(Level of (Leveling Hero)) Equal to 50
Actions
Item - Create Tome of Power at (Position of (Leveling Hero))
Hero - Give (Last created item) to (Leveling Hero)