Cheapest priced copy (Duskmourn: House of Horror): $0.35 at Card Kingdom, near mint, their price list as of .
Miasma Demon 
Creature — Demon · 5/4 · Uncommon · Duskmourn: House of Horror · #109
Flying
When this creature enters, you may discard any number of cards. When you do, up to that many target creatures each get -2/-2 until end of turn.
Legal inCommanderBrawlStandardPioneerModernLegacyVintage
Not legal inPauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Duskmourn: House of Horror | 109 | Uncommon | $0.35 | $0.49 |
One ruling from Wizards of the Coast
- 20 September 2024You don't choose targets for Miasma Demon's last ability at the time it triggers. Rather, a second "reflexive" ability triggers when you discard cards this way. You choose targets for that ability as it goes on the stack. Each player may respond to this triggered ability as normal.