Pyre of Heroes
Artifact
, 
, Sacrifice a creature: Search your library for a creature card that shares a creature type with the sacrificed creature and has mana value equal to 1 plus that creature's mana value. Put that card onto the battlefield, then shuffle. Activate only as a sorcery.
Piotr Dura
Kaldheim Promos (PKHM)
• #241sRulings
Once you announce that you're activating the activated ability, no player may take actions until the ability has been paid for. Notably, opponents can't try to remove one of your creatures to stop you from sacrificing it.
(wotc • 2021-02-05)
Use the creature types and mana value of the creature you sacrificed as it existed on the battlefield to determine what creature card you can find. Notably, if you sacrifice a creature that's a double-faced permanent with its back face up, you'll use the characteristics of the back face, not the front face.
(wotc • 2021-02-05)
If a permanent or a card in a library has {X} in its mana cost, X is considered to be 0.
(wotc • 2021-02-05)
Rulings
Once you announce that you're activating the activated ability, no player may take actions until the ability has been paid for. Notably, opponents can't try to remove one of your creatures to stop you from sacrificing it.
(wotc • 2021-02-05)
Use the creature types and mana value of the creature you sacrificed as it existed on the battlefield to determine what creature card you can find. Notably, if you sacrifice a creature that's a double-faced permanent with its back face up, you'll use the characteristics of the back face, not the front face.
(wotc • 2021-02-05)
If a permanent or a card in a library has {X} in its mana cost, X is considered to be 0.
(wotc • 2021-02-05)