msem-instigator

Storied spells you cast cost {1} less to cast. (Enchantments and legendary cards are storied.)

Hexproof

Haste
Sandstorm Sentinel enters with X +1/+1 counters on it, where X is your fealty to Deserts. (Each Desert you control counts toward your fealty to Deserts.)
Mirage {1}{R} (You may cast this spell as though it had flash for its mirage cost. If you do, sacrifice it at the beginning of the next cleanup step.)

Shimmer (Whenever this creature attacks, create a tapped and attacking token that's a copy of it. Exile the token at the beginning of the end step.)
When Sandstrider enters, put a +1/+1 counter on target creature.

Trample
You may cast Sandswim Titan from exile. If you do, it enters with three +1/+1 counters on it.

Choose two —
• Target player creates a 3/3 green Wurm creature token.
• Target player puts three +1/+1 counters on a creature they control.
• Return target permanent card from your graveyard to your hand.
• Destroy target creature with flying.

When Sandwurm's Might enters, you may have target creature you control fight target creature you don't control.
Each creature you control enters with an additional +1/+1 counter on it.

Flying
{1}{R}: Sangrite Dragon gets +2/+0 until end of turn.
Sacrifice another creature: Add {R}{R}.

Menace
Cycling {R} ({R}, Discard this card: Draw a card.)

Whenever you gain life, target opponent loses that much life.

Target creature gets -3/-3 until end of turn. You gain 3 life.

Flying, lifelink
Whenever you gain life, you may have target creature get -X/-X until end of turn, where X is the amount of life you gained.

Flash (You may cast this spell any time you could cast an instant.)
When Sanguine Muralist enters, you may have target creature's toughness become 1 until end of turn.

Flash
Poisonous 2 (Whenever this creature deals combat damage to a player, that player gets two poison counters. A player with ten or more poison counters loses the game.)
When Sankataar Ambusher enters, if an opponent is poisoned, Sankataar Ambusher gets +2/+2 until end of turn.

Poisonous 3 (Whenever this creature deals combat damage to a player, that player gets three poison counters.)
When Sankataar Assailant enters, choose a counter on target permanent or player. Give that permanent or player another counter of that kind.

Poisonous 5 (Whenever this creature deals combat damage to a player, that player gets five poison counters.)
At the beginning of your upkeep, if an opponent is poisoned, you may destroy target Human.

Trample

Menace
When Santriza Gang-Boss enters, it deals X damage to any target, where X is the number of Pirates and/or Rogues you control.

Whenever you cast a noncreature spell, Sara, Entelan Elementalist gets +X/+0 until end of turn, where X is Sara's power. It deals 1 damage to each creature you don't control.

If you would draw your first card each turn, instead draw two cards, then discard a card.
Whenever you draw an even numbered card in a turn, put a +1/+1 counter on Saraf, Tuned Disciple. (The second, fourth, sixth, etc.)

{B}, Pay 1 life: Target creature's controller sacrifices it unless that player pays 1 life.
{B}, Sacrifice a creature: You gain life equal to the sacrificed creature's power.

Flying
Improve—{1}{B/R}, Sacrifice a creature. ({1}{B/R}, Sacrifice a creature: Put a +1/+1 counter on this creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)
Whenever another creature you control dies, each opponent loses 1 life and you gain 1 life. If that creature was sacrificed, instead each opponent loses 2 life and you gain 2 life.

When Sarrutu Worldbinder enters, create two 1/1 red Elemental creature tokens.
{1}{U}, {T}: Elementals you control gain flying until end of turn.
{2}{R}, {T}: Elementals you control get +2/+0 until end of turn.

At the beginning of your upkeep, you gain 1 life for each color among permanents you control.
{W}{U}{B}{R}{G}, Sacrifice Sartha's Studies: Double your life total.

When Sasori Nightrunner enters, create a 2/2 colorless Spirit creature token.
Whenever a colorless creature you control dies, each opponent loses 1 life.