Scripts for beginners.

Good evening. I tried to activate the script: StartCombat (hero, Assasin, 3, CREATURE_SCOUT, 7 * 5, CREATURE_ASSASSIN, 7 * 5, CREATURE_WITCH, 5*4 ,nil, nil, nil, not nil)
It says: Value was NIL when getting global with name "Assasin"
The hero is created, and the script name is correct. I tried it both with and without a hero on the map. I added it to "AdventureMapPropetires/Heroes". The result is the same. What did I do wrong?