Because the Horn of Glory is inconveniently located in a corner of the arena, it is somewhat rarely used. Usually, the player that uses it is the second in their position.
On the 10th Wave, when the Penance Queen arrives, the Horn of Glory is blocked by rubble and cannot be used for the rest of the round.
The horn of glory is usually used in cases where one of the team players is idle or someone else is not functioning as expected by not calling an order to other player(s).
Unfortunately, the horn can also be abused by mischievous players to mislead other players.