Cheapest priced copy (The List): $27.99 at Card Kingdom, near mint, their price list as of .
Aetherflux Reservoir 
Artifact · Mythic · The Brothers' War Retro Artifacts · #2
Whenever you cast a spell, you gain 1 life for each spell you've cast this turn.
Pay 50 life: This artifact deals 50 damage to any target.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
6 printings · $27.99 to $69.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| The Brothers' War Retro Artifacts | 2 | Mythic | $29.99 | $54.99 |
| The Brothers' War Retro Artifacts | 65 | Mythic | $39.99 | $69.99Out of stock |
| The Brothers' War Retro Artifacts | 65z | Mythic | — | — |
| Kaladesh | 192 | Rare | $29.99 | $49.99 |
| Kaladesh Promos | 192s | Rare | — | $49.99 |
| The List | KLD-192 | Rare | $27.99 | — |
4 rulings from Wizards of the Coast
- 20 September 2016The first ability counts the spell that caused it to trigger plus any other spells you cast earlier in the turn.
- 20 September 2016The first ability counts spells you cast earlier in the turn even if you didn't control Aetherflux Reservoir as you cast them, and even if those spells were countered.
- 20 September 2016Aetherflux Reservoir's first ability doesn't trigger when you cast Aetherflux Reservoir itself.
- 20 September 2016The number of spells you've cast is counted only as Aetherflux Reservoir's triggered ability resolves. For example, if you cast a spell, then respond to the triggered ability with a second spell, you'll gain 4 life total.