PvP mode is a place where players can pit their squads of five Heroes against another player's squad in a real-time combat setting. Battles are one round, and end when all Heroes on the opposing team are knocked out. The two modes are Tournament and Free Play.
In Tournaments, the winner earns PvP Points, which increase your ranking in a PvP event, enabling you to reach higher Tier prizes. The loser doesn't lose points.
Winning five games lets you open a PvP Crate, which contains special items!
In Free Play mode, which is enabled between Tournaments, there is no rank, and play is merely for fun, practice, and to earn PvP Crates.
PvP matches do not take energy. When one of your Heroes is knocked out, they lose a life. You're free to keep playing PvP until your lives are gone and you can no longer field Heroes. Lives reset on a daily timer.
You can also challenge other players to PvP Duels. These 1v1 matches use the Heroes you've unlocked, set to any Grade the host decides, and you can play on any Map! Tap on a player's name to challenge them. These PvP Duels take no energy, and provide no rewards. They're just for fun!