Can Sprite Call be used during an attack to play an additional attacker at a battlefield you don't control?

Ruling: No, you cannot play units at a battlefield you don't control. You can use Sprite Call for defense, or play the sprites beforehand and move them in with your other attacking units.

Sequence:

• Play sprites before the attack
• Move them to the battlefield with other attacking units

Nuances:

• Sprites enter ready, so they can be played before attacking and then moved in
• You cannot play them retroactively in response to opponent actions like buffing their units