Cheapest priced copy (Commander 2021): $0.99 at Card Kingdom, near mint, their price list as of .
Combustible Gearhulk 
Artifact Creature — Construct · 6/6 · Mythic · Modern Horizons 3 Commander · #210
First strike
When this creature enters, target opponent may have you draw three cards. If the player doesn't, you mill three cards, then this creature deals damage to that player equal to the total mana value of those cards.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
11 printings · $0.99 to $109.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2021 | 163 | Mythic | $0.99 | — |
| Aetherdrift Commander | 102 | Mythic | $0.99 | — |
| Duskmourn: House of Horror Commander | 163 | Mythic | $0.99 | — |
| Final Fantasy Commander | 292 | Mythic | $0.99 | $0.99 |
| Kaladesh | 112 | Mythic | $1.49 | $5.99 |
| Modern Horizons 3 Commander | 210 | Mythic | $0.99 | $2.49 |
| Kaladesh Inventions | 4 | Special | — | $109.99 |
| Kaladesh Promos | 112p | Mythic | $1.99 | $9.99Out of stock |
| Kaladesh Promos | 112s | Mythic | — | $9.99 |
| The List | KLD-112 | Mythic | $1.29 | — |
| Starter Commander Decks | 128 | Mythic | $0.99 | — |
3 rulings from Wizards of the Coast
- 20 September 2016If any of the cards put into your graveyard have {X} in their mana cost, X is considered to be 0.
- 20 September 2016While Combustible Gearhulk's triggered ability is resolving, no player may take any actions other than those specified by the Gearhulk. Once the opponent makes a choice, players can't cast spells or activate abilities until after the cards are drawn or put into the graveyard and damage has been dealt (if applicable).
- 20 September 2016If you have fewer than three cards in your library, the opponent may choose to have you draw three cards. If so, you'll lose the game as state-based actions are performed.