[webfischi]

It looks like I'm the first who was able to catch that bug. When you attack, the damage is indefinite (zero).

The code for this mask is in arena.lua line 859-884 and looks like this:

  -- маска Зависти
	if hero_item_count2("sp_bonus_level_damage", "count") > 0 then
		if attacker ~= nil and receiver ~= nil and damage > 0 then
			local atk_level = Attack.act_level(attacker)
			if Attack.act_feature(attaker,"pawn") then 
				atk_level = 3
				if Attack.act_feature(attaker,"boss") then
					atk_level = 5
				end
			end
			
			local rec_level = Attack.act_level(receiver)
			if Attack.act_feature(receiver,"pawn") then 
				rec_level = 3
				if Attack.act_feature(receiver,"boss") then
					rec_level = 5
				end
			end
			
			if atk_level > rec_level then
				damage = damage * (1 + (atk_level - rec_level) * hero_item_count2("sp_bonus_level_damage", "count")/100)
				addrage = addrage * (1 + (atk_level - rec_level) * hero_item_count2("sp_bonus_level_damage", "count")/100)
			end
			
		end
	end

Edit: After further investigation, the game doesn't get anything from the "damage" equation, I added a line that should set damage to 1 no matter what solution was calculated earlier, and the game still says 0, so I guess it is missing some kind of return value.