Cheapest priced copy (Urza's Saga): $0.35 at Card Kingdom, near mint, their price list as of .
Skittering Skirge 
Creature — Phyrexian Imp · 3/2 · Common · Urza's Saga · #158
Flying
When you cast a creature spell, sacrifice this creature.
Legal inCommanderLegacyVintagePauper
Not legal inBrawlStandardPioneerModern
3 printings · $0.35 to $24.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Beatdown Box Set | 31 | Common | $0.59 | — |
| Arena League 1999 | 4 | Rare | — | $24.99 |
| Urza's Saga | 158 | Common | $0.35 | — |
2 rulings from Wizards of the Coast
- 4 October 2004The triggered ability triggers when the creature spell is cast, and it is put on the stack before any responses can be cast or activated. This ability will resolve before that creature enters.
- 1 April 2008A "creature spell" is any spell with the type Creature, even if it has other types such as Artifact or Enchantment. Older cards of type Summon are also Creature spells.