Aetherflux Reservoir [Kaladesh] U-WTR082 it becomes an Aura with

it becomes an Aura with "enchant creature put onto the battlefield with Necromancy

Pay 1 life: Exile the top card of your library face down

Set: Limited Edition Alpha Type: Creature — Hydra Rarity: Rare Cost: {X}{R}{R} Rock Hydra enters the battlefield with X +1/+1 counters on it

His assistants calculate the amount of the tribute

Aetherflux Reservoir [Kaladesh] U-WTR082 it becomes an Aura withSet: Kaladesh Type: Artifact Rarity: Rare Cost: {4} Whenever you cast a spell, you gain 1 life for each spell you've cast this turn. Pay 50 life: Aetherflux Reservoir deals 50 damage to any target. While most power is used for ordinary, everyday tasks, one shouldn't underestimate its potential for the extraordinary.