Cheapest priced copy (Edge of Eternities): $4.99 at Card Kingdom, near mint, their price list as of .
Mightform Harmonizer 
Creature — Insect Druid · 4/4 · Rare · Edge of Eternities · #297
Landfall — Whenever a land you control enters, double the power of target creature you control until end of turn.
Warp {2}{G} (You may cast this card from your hand for its warp cost. Exile this creature at the beginning of the next end step, then you may cast it from exile on a later turn.)
Legal inCommanderBrawlStandardPioneerModernLegacyVintage
Not legal inPauper
4 printings · $3.99 to $8.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Edge of Eternities | 200 | Rare | $4.99 | $3.99 |
| Edge of Eternities | 297 | Rare | $5.99 | $8.99 |
| Edge of Eternities Promos | 200p | Rare | $4.99 | $4.99Out of stock |
| Edge of Eternities Promos | 200s | Rare | — | $5.49 |
2 rulings from Wizards of the Coast
- 25 July 2025If an effect instructs you to “double” a creature’s power, that creature gets +X/+0, where X is its power as that effect begins to apply. Similarly, a creature whose toughness is doubled gets +0/+X, where X is its toughness as the effect begins to apply.
- 25 July 2025If a creature’s power is less than 0 when it’s doubled, instead that creature gets -X/-0, where X is how much less than 0 its power is. For example, if an effect has given Bear Cub, a 2/2 creature, -4/-0 so that it’s a -2/2 creature, doubling its power and toughness gives it -2/+2, and it becomes a -4/4 creature.