Cheapest priced copy (Double Masters): $0.35 at Card Kingdom, near mint, their price list as of .
Lightning Axe 
Instant · Uncommon · Shadows over Innistrad · #170
As an additional cost to cast this spell, discard a card or pay {5}.
Lightning Axe deals 5 damage to target creature.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
9 printings · $0.35 to $4.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Double Masters | 135 | Common | $0.35 | $0.49 |
| Innistrad Remastered | 162 | Uncommon | $0.35 | $0.49 |
| Innistrad Remastered | 398 | Uncommon | $0.99 | $4.49 |
| Jumpstart 2022 | 569 | Uncommon | $0.35 | — |
| Jumpstart | 341 | Uncommon | $0.35 | — |
| The List | TSP-168 | Common | $0.35 | — |
| Shadows over Innistrad | 170 | Uncommon | $0.35 | $0.79 |
| Time Spiral | 168 | Common | $0.39 | $2.49 |
| Time Spiral Remastered | 174 | Uncommon | $0.35 | $1.99 |
One ruling from Wizards of the Coast
- 19 March 2021The mana value of Lightning Axe is 1, no matter which additional cost you paid.