FOILCheapest priced copy (Commander Masters): $2.79 at Card Kingdom, near mint, their price list as of .
Spiteful Sliver 
Creature — Sliver · 2/2 · Rare · Secret Lair Drop · #643
Sliver creatures you control have "Whenever this creature is dealt damage, it deals that much damage to target player or planeswalker."
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
3 printings · $2.79 to $20.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander Masters | 881 | Rare | $2.79 | — |
| Modern Horizons | 148 | Rare | $2.79 | $7.99 |
| Secret Lair Drop | 643 | Rare | — | $20.99 |
3 rulings from Wizards of the Coast
- 14 June 2019Damage dealt by the Sliver due to its triggered ability isn’t combat damage, even if it was combat damage that caused that ability to trigger.
- 14 June 2019If a Sliver is dealt damage by multiple sources at once (such as by two creatures blocking it), its ability triggers once and one target is dealt that much damage.
- 14 June 2019The ability granted by Spiteful Sliver will trigger even if the Sliver is dealt lethal damage. For example, if a 2/2 Sliver blocks a 7/7 creature, the Sliver’s ability will trigger and it will deal 7 damage.