@unique.spectral
Please do write in the thread instead of in a PM if it concerns the problem.
If you want to say somethin that should only be seen by me then use a PM.
On-Topic:
You have to find out when a boss dies.
"If dying unit is a hero equal to true" doesn't work for that because your heroes (which you want to level) are then also counted as bosses.
The best way to do this is make an unit group (BossesGroup) and put all bosses inside that group.
Event -> A unit dies.
Condition -> Triggering unit is in BossesGroup equal to true
Actions ->
Pick every unit in playable map area.
- If picked unit is a hero Then
---- Hero - Set (picked unit) Hero-Level to (Hero-Level of (picked unit) + 2), Show level-up graphics
All those things are in GUI