Doomsday [Masters 25] SM161 you cannot Special Summon monsters

you cannot Special Summon monsters from the Extra Deck

Set: Aether Revolt Prerelease Promos Type: Artifact Creature — Construct Rarity: Rare Cost: {X}{X} Walking Ballista enters the battlefield with X +1/+1 counters on it

(The next time that creature would be destroyed this turn

except "Stellarknight Constellar Diamond"

When you cast a creature spell

Doomsday [Masters 25] SM161 you cannot Special Summon monstersSet: Masters 25 Type: Sorcery Rarity: Mythic Cost: {B}{B}{B} Search your library and graveyard for five cards and exile the rest. Put the chosen cards on top of your library in any order. You lose half your life, rounded up.