i was thinking if this is a bug, and if more people is seeing this happening
Ground based skills usually cant hit flying monsters. Flame ground is one of them. Intended by game design.
Just be happy your a mage and can do something about it. Cleric life is hard if you dont go priest or krivis early.
you can go Bokor instead and abuse Hex + Effigy =)
As @nizidr said, it cant hit “flying” monsters.
Now I use the term loosely because of the fact some monsters and bosses do indeed seem to be floating or flying and still get hit by it.
boss always get hit no matter if they are flying or not iirc
aside from that normal and elite flying cant be hit by flame ground
Oh okay makes sense i didnt know that ty.
2 bad lol cleric life is hard we cant hit flying mobs for a long time
Flame ground. Flying mobs aren’t on the ground 
Frost Cloud. Flying mobs aren’t on the… wait. 
But you still have a point here, that are some floating enemies that aren’t registered as flying. You can see as Archers don’t do double damage (bow attribute) to them. 
you forgot “Rain” that cannot hit flying mobs also.
Yep, Rain was th e best honestly ROFL…
