Cheapest priced copy (Adventures in the Forgotten Realms): $0.49 at Card Kingdom, near mint, their price list as of .
Skeletal Swarming 
Enchantment · Rare · Adventures in the Forgotten Realms · #389
Each Skeleton you control has trample, attacks each combat if able, and gets +X/+0, where X is the number of other Skeletons you control.
At the beginning of your end step, create a tapped 1/1 black Skeleton creature token. If a creature died this turn, create two of those tokens instead.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
5 printings · $0.49 to $8.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Adventures in the Forgotten Realms | 232 | Rare | $0.49 | $0.49 |
| Adventures in the Forgotten Realms | 389 | Rare | $0.49 | $0.49 |
| Adventures in the Forgotten Realms Promos | 232a | Rare | — | $8.49Out of stock |
| Adventures in the Forgotten Realms Promos | 232p | Rare | $0.49 | $0.49 |
| Adventures in the Forgotten Realms Promos | 232s | Rare | — | $2.99Out of stock |