Cheapest priced copy (The Brothers' War Retro Artifacts): $1.99 at Card Kingdom, near mint, their price list as of .
Quietus Spike 
Artifact — Equipment · Rare · Shards of Alara · #217
Equipped creature has deathtouch.
Whenever equipped creature deals combat damage to a player, that player loses half their life, rounded up.
Equip {3}
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
8 printings · $1.99 to $6.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Shards of Alara | 217 | Rare | $2.49 | $6.99 |
| The Brothers' War Retro Artifacts | 46 | Rare | $1.99 | $2.99 |
| The Brothers' War Retro Artifacts | 109 | Rare | $1.99 | $4.49 |
| The Brothers' War Retro Artifacts | 109z | Rare | — | — |
| Commander 2017 | 220 | Rare | $2.49 | — |
| New Capenna Commander | 377 | Rare | $2.29 | — |
| Planechase 2012 | 112 | Rare | $2.49 | — |
| Planechase Anthology | 112 | Rare | $2.49 | — |
3 rulings from Wizards of the Coast
- 1 October 2008That player loses half their 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.
- 1 October 2008If multiple Quietus Spikes trigger at the same time, that player loses half their 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.
- 15 June 2010In a Two-Headed Giant game, after combat damage is dealt, Quietus Spike looks at that player's life total (which is the same as the team's life total) when determining how much life the team will lose, which basically means the team's life total is halved. Here's an example of the math: The team has 19 life, so the player has 19 life. Quietus Spike causes the team to lose 10 life (19 divided by 2, rounded up). The team's life total becomes 9 (19 minus 10).