League-of-legends – What do these signs mean League of Legends

An ace occurs when the last player of the opposing team dies. It means that all 5 of them are dead at the same time, whether it be for 1 second or much longer. The ace is attributed to whoever scores the killing blow on the last champion to die, although there is no extra bonus for it.

If you get an ace during a team fight in late game, usually you can push and win the game right then and there. Other times, you get an ace by killing their lone defender right before the other 4 of them spawn, in which case it's less meaningful.

The immediate exploit I can think of is destroying Teemo's mushrooms. Since they last for 10 minutes, a spectator could direct a player with an oracle's where to go to clear them.

A spectator could also help keep track of buff respawns, though this is typically handled by the jungler.

Though not directly useful, a spectator can watch a player's play-style and make best guesses about future moves. Any pattern they see could potentially be used against that player.