Text (LG+errata): {Tap}, Sacrifice ~this~: Exchange life totals with target opponent. Activate this ability only during your upkeep. [Oracle 2009/07/08]
The life total trade is treated as if one player loses life and the other one gains life. Things that trigger off gain or loss of life will trigger. [bethmo 1996/12/07] For example, if player A has 5 life and player B has 10 life, the Mirror's effect will cause player A to gain 5 life and player B to lose 5 life. Effects like Forsaken Wastes can prevent the life gain.
If one player is a Lich, they are considered to be gaining life from this effect and instead draw cards. The other player is in deep trouble if they cannot raise their life points from zero. [Aahz 1994/06/16]
If a player has a negative life, the swap considers the player to be at zero life for purposes of what total the other player gets. [WotC Rules Team 1996/12/03] The player's actual life total is used to determine how much life they gain.
Vintage tournaments (see Rule 911) restricted this card from 1994/08/01 until 1999/10/01.
Legacy tournaments (see Rule 912) banned this card until 1999/10/01.
Extended tournaments (see Rule 913) have always banned this card.
Standard (Type 2) tournaments (see Rule 914) have always banned this card, since it is not part of the environment.
