When Magister Sphinx enters the battlefield, target player's life total becomes 10.
2/1/2009 This ability is not optional.
2/1/2009 For a player’s life total to become 10, what actually happens is that the player gains or loses the appropriate amount of life. For example, if the targeted player’s life total is 4 when this ability resolves, it will cause that player to gain 6 life; alternately, if the targeted player’s life total is 17 when this ability resolves, it will cause that player to lose 7 life. Other cards that interact with life gain or life loss will interact with this effect accordingly.
6/15/2010 In a Two-Headed Giant game, this ability basically causes the team’s life total to become 10, but only the targeted player is considered to have actually gained or lost life.