Aether Herder (AER) from Aether Revolt, available at 401 Games Canada.

• Rarity: Common
• Finish: Normal
• Artist: Victor Adame Minguez
• Card Text:
  When Aether Herder enters the battlefield, you get EE (two energy counters).
  Whenever Aether Herder attacks, you may pay EE. If you do, create a 1/1 colorless Servo artifact creature token.