Can you play a card to hidden from your deck instead of hand? Like if revealed by Reksai legend?
No, you cannot.
According to the RiftJudge FAQ #9502 and FAQ #10392, you cannot use the Rek'Sai (Void Burrower) legend ability to "Hide" a card.
Here is the breakdown of why this interaction does not work:
- Hiding is a distinct Discretionary Action: As defined in Rule 421.2 and Rule 811.1.c.1, "Hide" is a specific Discretionary Action. It is not the same thing as "Playing" a card.
- Prerequisites for Hiding: The Hidden keyword (Rule 811.1.b) specifically allows you to hide a card only while that card is in your hand or your Champion Zone.
- Rek'Sai's Ability: The Void Burrower legend ability instructs you to reveal cards from your Main Deck and then play one of them. Because the card is being played from your Main Deck—not your hand or Champion Zone—you do not meet the prerequisites to perform the "Hide" action.
Because Rek'Sai's ability specifically instructs you to play the card, you must play the selected card as a spell or unit (paying its costs as normal) rather than attempting to hide it.