msem-instigator

You may exert Deathmarked Explorer as it attacks. When you do, it gets +X/+X until end of turn, where X is 10 minus your life total. (An exerted creature won't untap during your next untap step.)
{T}, Discard a card: Draw a card. Deathmarked Explorer deals 2 damage to you.

Menace
When a card leaves your graveyard, exile the top card of your library. You may play that card until the end of your next turn.

Indestructible (Damage and effects that say “destroy” don't destroy this creature.)
Whenever Declare, the Mother Bear deals combat damage to a player, put a +1/+1 counter on it.

Menace
Creatures you control get +1/+0 as long as you've foretold a card this turn.
Creatures you control get +1/+0 as long as you've cast a foretold spell this turn.

Whenever you cast a spell, if it shared a color with the last spell you cast this turn, put two +1/+1 counters on Defected Android.

Augmented — At the beginning of each end step, if you've spent {W}{U}{B}{R}{G} to cast spells this turn, put a +1/+1 counter on Defected Explorer.

Flying, vigilance
Whenever you attack, if you've cast a spell from a graveyard this turn, you may pay {1}{W}. If you do, put Defender of Carü Mapu from your graveyard onto the battlefield. It's attacking.

Creatures you don't control get -1/-0 as long as their controller is cursed.

{4}{B}: Depthlight Beacon gets +1/+1 and gains lifelink until end of turn.
Cycling {2/B} ({2/B}, Discard this card: Draw a card.)

Menace
Other artifact creatures you control have menace.
{2}{B}{R}: Salvage an artifact or creature card. (Exile one from your graveyard until this creature leaves the battlefield. Whenever this creature deals combat damage to a player, put a card it salvaged into your hand.)

{B}, Sacrifice another creature: Deranged Apothecary gains indestructible until end of turn.

Frenzy 3 (Whenever this creature attacks and isn't blocked, it gets +3/+0 until end of turn.)
Other red creatures you control have frenzy 2. (If a creature has multiple instances of frenzy, each triggers separately.)
Other creatures you control have frenzy 1.

Distorted (This creature can be blocked by tapped creatures but not untapped creatures.)

Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.)
{2}, Sacrifice a creature: Put a +1/+1 counter on Desert Marauder.

Prowess
At the beginning of combat on each of your turns, you may draw a card. If you do, discard a card.

Menace
Whenever Despair Scavenger attacks, you may have target creature get -1/-1 until end of turn.

When Desperate Botanist enters, create a 0/1 green Plant creature token with “{T}: Add {G}.”
{5}{G}: Transform Desperate Botanist. Activate only if it's attacking.

{1}, Sacrifice a creature: Desperate Forsaken gets +1/+1 until end of turn. You gain 1 life.

Sacrifice a land: Desperate Ravager gets +2/+0 and gains haste until end of turn.

As an additional cost to cast this spell, pay {2} or sacrifice a creature.
Flying, vigilance

Haste
Fleeting {B} (You may cast this spell for its fleeting cost. If you do, sacrifice it at the beginning of the next end step.)

Assault {1}{B} (Whenever this attacks, if it has no +1/+1 counters on it, you may pay its assault cost to put a +1/+1 counter on it.)
Whenever a creature you control assaults, you may have target creature get -2/-2 until end of turn.

Flying
Whenever another creature dies, each opponent loses 1 life and you gain 1 life.

Whenever a storied permanent you control enters, you gain 1 life and each opponent loses 1 life. (Enchantments and legendary permanents are storied.)