Alchemist's Gambit

Cleave {4}{U}{U}{R} (You may cast this spell for its cleave cost. If you do, remove the words in square brackets.)
Take an extra turn after this one. During that turn, damage can't be prevented. [At the beginning of that turn's end step, you lose the game.]
Exile Alchemist's Gambit.

Devilish Valet

Trample, haste
Alliance — Whenever another creature you control enters, double this creature's power until end of turn.

Sneak Attack

{R}: You may put a creature card from your hand onto the battlefield. That creature gains haste. Sacrifice the creature at the beginning of the next end step.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control. It can attack and {T} no matter when it came under your control.)
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Armor of Shadows

Until end of turn, target creature gets +1/+0 and gains indestructible. (Damage and effects that say "destroy" don't destroy it.)

Red Sun's Twilight

Destroy up to X target artifacts. If X is 5 or more, for each artifact destroyed this way, create a token that's a copy of it. Those tokens gain haste. Exile them at the beginning of the next end step.

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Battle-Rage Blessing

Target creature gains deathtouch and indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Ideas Unbound

Draw three cards. Discard three cards at the beginning of the next end step.

Offer Immortality

Obeka, Brute Chronologist

{T}: The player whose turn it is may end the turn. (Exile all spells and abilities from the stack. The player whose turn it is discards down to their maximum hand size. Damage wears off, and "this turn" and "until end of turn" effects end.)