Restless Reef
Land
This land enters tapped.
: Add 
or 
.
: Until end of turn, this land becomes a 4/4 blue and black Shark creature with deathtouch. It's still a land.
Whenever this land attacks, target player mills four cards.
Hristo D. Chukov
Rulings
If this becomes a creature because of an effect other than its own ability, its last ability will still trigger whenever it attacks.
(wotc • 2023-11-10)
If this becomes a creature but you haven't controlled it continuously since your most recent turn began, you won't be able to activate its mana ability or attack with it that turn.
(wotc • 2023-11-10)
Rulings
If this becomes a creature because of an effect other than its own ability, its last ability will still trigger whenever it attacks.
(wotc • 2023-11-10)
If this becomes a creature but you haven't controlled it continuously since your most recent turn began, you won't be able to activate its mana ability or attack with it that turn.
(wotc • 2023-11-10)