He passed over Udûn and Gorgoroth and saw all the land in ruin and tumult beneath him, and before him Mount Doom blazing, pouring out its fire.

Landroval, Horizon Witness

Flying
Whenever two or more creatures you control attack a player, target attacking creature without flying gains flying until end of turn.

The Lord of the Rings: Tales of Middle-earth

In a multiplayer game, Landroval, Horizon Witness's triggered ability triggers once for each player you attack with at least two creatures.

Two or more creatures you control must attack the same player in order for Landroval, Horizon Witness's ability to trigger. Creatures you control that attack planeswalkers that player controls or battles that player is protecting won't count toward Landroval, Horizon Witness's trigger condition.