Heroes 4 map editor - units pool

[Berhaciarz]

Hello!
I joined this community because no matter where I search I can't find a solution to my problem. I decided to create my own map so I can play it with my friend. When I place random level 4 creature unit (the neutral unit on map) it spawns random level 4 unit, which is fine most of the times, but sometimes the game decides to spawn level 4 units but from winds of war expansion (for eg. megadragons). I tried opening zanfas's challenge to check how on that map the unit pool is only from base game but I can't figure it out. What I would like to do is to disable expansions units spawns and if its possible keep artifacts.
I will be extremely grateful if someone can help me out!