If I control both battlefields with a unit at each, and my opponent attacks battlefield A, can I use Arcane Shift during the showdown to banish my unit from battlefield B and play it to battlefield A?

Ruling: Yes, you can use Arcane Shift to banish your friendly unit from battlefield B and play it directly to battlefield A, as long as you control battlefield A and can target an enemy unit at a battlefield for the damage portion of the spell.

Sequence:

• Play Arcane Shift during the showdown at battlefield A
• Banish your friendly unit from battlefield B
• Play the banished unit to battlefield A (which you control)
• Deal 3 damage to an enemy unit at a battlefield

Nuances:

• Arcane Shift has no location requirement for where the friendly unit must be when targeted or where it can be played to
• You can play units to any battlefield you control
• The damage requirement targets an enemy unit at a battlefield, but this is separate from the friendly unit's location