Artifact, 6 (6) {T}, Sacrifice Mirror Universe: Exchange life totals with target opponent. Play this ability only during your upkeep.1
Illus. Phil Foglio
9/16/2007: When the life totals are exchanged, each player gains or loses the amount of life necessary to equal the other player's previous life total. For example, if Player A has 5 life and Player B has 3 life before the exchange, Player A will lose 2 life and Player B will gain 2 life. Replacement effects may modify these gains and losses, and triggered abilities may trigger on them.