Yennett, Cryptic Sovereign [Commander 2018] Starter Deck during damage calculation you can

during damage calculation you can send 1 card (only) from your hand to the Graveyard to have this card gain 600 ATK during damage calculation only

" —Speaker Trifon

shuffle the targets from your Graveyard into the Deck

you can detach 1 Xyz Material from that monster instead

Set: Modern Masters 2015 Type: Instant Rarity: Mythic Cost: {X}{R}{R} Multikicker {1} (You may pay an additional {1} any number of times as you cast this spell

Yennett, Cryptic Sovereign [Commander 2018] Starter Deck during damage calculation you canSet: Commander 2018 Type: Legendary Creature Sphinx Rarity: Mythic Cost: {2}{W}{U}{B} Flying, vigilance, menace Whenever Yennett, Cryptic Sovereign attacks, reveal the top card of your library. You may cast it without paying its mana cost if its mana value is odd. If you don't cast it, draw a card. She talks using riddles her disciples alone can unravel.