If a player has a hidden card on the battlefield and one unit, and that unit is moved back to their base using Charm, do they still control the battlefield and what happens to the hidden card?

Ruling: If a player no longer has a unit on the battlefield, they no longer control it and the hidden card is discarded.

Nuances:

• The player can use the hidden card as a reaction to the Charm before losing battlefield control
• If they don't use it as a reaction, the hidden card gets trashed