Tezzeret the Schemer

[+1]: Create a colorless artifact token named Etherium Cell with "{T}, Sacrifice this artifact: Add one mana of any color."
[−2]: Target creature gets +X/-X until end of turn, where X is the number of artifacts you control.
[−7]: You get an emblem with "At the beginning of combat on your turn, target artifact you control becomes an artifact creature with base power and toughness 5/5."

Kaladesh Remastered

+1: Create a colorless artifact token named Etherium Cell with "{T}, Sacrifice this artifact: Add one mana of any color."
−2: Target creature gets +X/-X until end of turn, where X is the number of artifacts you control.
−7: You get an emblem with "At the beginning of combat on your turn, target artifact you control becomes an artifact creature with base power and toughness 5/5."

Aether Revolt

+1: Create a colorless artifact token named Etherium Cell with "{T}, Sacrifice this artifact: Add one mana of any color to your mana pool."
−2: Target creature gets +X/-X until end of turn, where X is the number of artifacts you control.
−7: You get an emblem with "At the beginning of combat on your turn, target artifact you control becomes an artifact creature with base power and toughness 5/5."

Aether Revolt Promos

A Vehicle targeted by the emblem’s ability becomes a 5/5 creature. Crewing it won’t change its power and toughness.

An artifact creature targeted by the emblem’s ability becomes 5/5 instead of its normal power and toughness.

An artifact that becomes a creature due to the emblem’s ability can’t attack unless you’ve controlled it continuously since your turn began. It doesn’t matter whether or not it was a creature at that time.

If an Equipment becomes a creature, it becomes unattached and it can’t be attached to a creature.

The effect of the emblem’s triggered ability lasts indefinitely.

The value of X for Tezzeret’s second ability is determined only as the ability resolves. It won’t change later in the turn if the number of artifacts you control changes.