Hidden
If Hidden gives a card Reaction, can I play it immediately after hiding it?
Hidden cards wait until the next turn
RiftPal explanation · Answer first
Actually
The normal permission to play a card from starts on the next turn. You cannot use it during the turn you hide the card.
RiftPal explanation
Why it matters
Hiding is not playing a card and does not start a ChainAn off-board zone that holds cards and abilities during the process of playing them. Cards and abilities on it are public information.View in Glossary . ReactionA timing keyword that includes Action's permissions and also permits a card or activated ability while a Chain is waiting. You still need the proper opportunity, normally Priority; it does not allow an interruption halfway through resolution.View in Glossary changes when you may play the hidden card, but does not remove the next-turn restriction. The next turn can be an opponent’s turn: you do not have to wait for your own next turn, provided the other play requirements are met.