If my opponent plays Bullet Time when I have Embermonk and a hidden Teemo on my battlefield (outside of combat), does it kill the monk and then allow me to play Teemo, or does it kill the monk and prevent me from playing Teemo?

Ruling: Outside of combat, if Bullet Time kills your only unit at a battlefield, the hidden card goes to trash during spell cleanup and you cannot play Teemo. You lose control of the battlefield when your last unit dies.

Sequence:

• Bullet Time resolves and deals damage
• Embermonk dies if enough damage is dealt
• Hidden Teemo is put in trash during cleanup of the spell
• You lose control of the battlefield

Nuances:

• During combat, you could pass priority and reveal Teemo before Bullet Time resolves to keep the battlefield
• You do not know how much damage Bullet Time will deal until it resolves (value is decided during resolution)
• Just because your only unit at a battlefield dies does not mean combat ends or you lose control during a showdown