10/1/2008: That player loses half his or her life after combat damage has been subtracted from the player's life total. The amount of life the player loses is determined as the triggered ability resolves.
10/1/2008: If multiple Quietus Spikes trigger at the same time, that player loses half his or her life when the first ability resolves, then loses half of the remainder when the next ability resolves, and so on. The player does not lose the same amount each time.
10/1/2008: In a Two-Headed Giant game, if a creature equipped with Quietus Spike would assign combat damage to the defending team, its damage is assigned to only one of the defending players. After combat damage is dealt, Quietus Spike looks at that player's share of the team's life total (the team's life total divided by two, rounded up) when determining how much life the team will lose. Here's an example of the math: The team has 19 life. The player's share is 10 life (19 divided by 2, rounded up). Quietus Spike causes the team to lose 5 life (10 divided by 2). The team's life total becomes 14 (19 minus 5).
Shards of Alara
(Rare)