Cheapest priced copy (Commander 2018): $0.69 at Card Kingdom, near mint, their price list as of .
Thopter Assembly 
Artifact Creature — Thopter · 5/5 · Rare · Mirrodin Besieged · #140
Flying
At the beginning of your upkeep, if you control no Thopters other than this creature, return this creature to its owner's hand and create five 1/1 colorless Thopter artifact creature tokens with flying.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
5 printings · $0.69 to $1.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2018 | 226 | Rare | $0.69 | — |
| Duel Decks: Elves vs. Inventors | 63 | Rare | $0.79 | — |
| Mirrodin Besieged | 140 | Rare | $0.79 | $1.99Out of stock |
| March of the Machine Commander | 386 | Rare | $0.79 | — |
| Mirrodin Besieged Promos | 140★ | Rare | — | $1.29 |
One ruling from Wizards of the Coast
- 1 June 2011The triggered ability looks for any permanent you control with the creature type Thopter, not just the Thopter tokens previously created by a Thopter Assembly.