Cheapest priced copy (Foundations): $0.35 at Card Kingdom, near mint, their price list as of .
Mold Adder 
Creature — Fungus Snake · 1/1 · Uncommon · Foundations · #640
Whenever an opponent casts a blue or black spell, you may put a +1/+1 counter on this creature.
Legal inCommanderBrawlStandardPioneerModernLegacyVintage
Not legal inPauper
2 printings · $0.35 to $4.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Foundations | 640 | Uncommon | $0.35 | — |
| Magic 2010 | 194 | Uncommon | $0.35 | $4.49 |
2 rulings from Wizards of the Coast
- 8 November 2024If an opponent casts a spell that's both blue and black, Mold Adder's ability triggers only once.
- 8 November 2024Mold Adder's ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered or otherwise leaves the stack without resolving.