D-oh... But you mean which kind of invisible mob:
1) Mob that attacks you, takes damage from you has label and is invisible
2) Mob that is invisible, ignores you and doesn't take damage from you
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Invisible monsters, they cannot be damaged. It happens that the monster disappears and appears "transparent". But this in my opinion does not happen so often. I saw a stone golem on the 3rd map like this, but for a long time a go.(2-3weeks).
my game id 1194765