Legend teams are special teams that appear during a Legend Challenge.
Each Legend team features different players, formations and rewards.
There are also Rare Legend Teams!
You will see a time limit at the bottom left of the Legend Challenge Menu screen.
If this time limit reaches zero before you choose to play or quit a match, the Legend team will leave and you won't be able to play a Legend Challenge until the next time they appear.
If you decide to challenge them, be sure to tap 'PLAY!' before the timer runs out.