msem-instigator

Whenever a land creature you control deals combat damage to a player, put a +1/+1 counter on it.
{1}{G}: Put a +1/+1 counter on target land you control. It becomes a 0/0 Elemental creature that's still a land.

Menace (This creature can't be blocked except by two or more creatures.)
Whenever Sagi's Revenant deals combat damage to a player, that player discards a card.
Whenever an opponent discards a land card, you may have target creature get -2/-2 until end of turn.

Vigilance
{1}{G}{G}: Sahalia Dragoons gets +4/+4 until end of turn. Activate only once each turn.

Trample, haste
When Sahra, the Consuming enters or attacks, sacrifice a permanent.
At the beginning of your end step, transform Sahra unless you've sacrificed two or more permanents this turn.

[+1]: Untap up to two target permanents. They gain hexproof until your next turn.
[–2]: Tap up to three target permanents. They don't untap during their controller's next untap step.
[–6]: Exile up to five target permanents. Return those cards to the battlefield under your control.

[+1]: Scry 1, then draw a card. You lose 1 life.
[–2]: Target player sacrifices a creature, then loses life equal to the greatest power among creatures they control.
[–5]: Choose a nonland card name. Exile all creatures and planeswalkers with that name, then search target player's graveyard, hand, and library for any number of cards with that name and exile them. That player shuffles.

Sammel Wyldjack enters with a fuse counter on him.
At the beginning of your upkeep, remove a fuse counter from Sammel Wyldjack. If you do, each player sacrifices four lands and Sammel Wyldjack deals 4 damage to each other creature.

When Sandbluff Enforcers enters, detain target creature an opponent controls. (Until your next turn, that creature can't attack or block and its activated abilities can't be activated.)

When Sandborn Mage enters, you may return target instant or sorcery card from your graveyard to your hand.
Mirage {2}{U}{U} (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.)

When Sandmouth Dragon enters, another target creature you control gets +3/+0 until end of turn.
Mirage {2}{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.)

Hexproof

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.

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.

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.

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.

Other creatures you control that entered this turn have haste and lifelink.
{T}: You may put a creature card from your hand onto the battlefield.

Golden age (If you cast an instant or sorcery spell, activated a nonmana ability, and attacked this turn, enter a renaissance for this game.)
Search your library for up to three creature cards with different mana values 4 or less, reveal them, put them into your hand, then shuffle. If you're in a renaissance, you may put one of those cards onto the battlefield instead of into your hand.

When Savannah Huntsman enters, it deals X damage to target creature or planeswalker, where X is the number of counters among permanents you control.

Untap all creatures and lands you control during each other player's untap step.
Ascend {4}{R}{R}{R} ({4}{R}{R}{R}: Exile this creature, then return it to the battlefield transformed. Ascend only as a sorcery.)

Each instant and sorcery card in your graveyard has reprise. The reprise cost is equal to its mana cost. (As you cast an instant or sorcery spell, you may exile one card with reprise from your graveyard and pay its reprise cost. If you do, add its effects to that spell.)
Reprising spells you control can't be countered.

As long as you control exactly two creatures, those creatures get +2/+1 and have lifelink.