msem-instigator

Assault {2}{R}{G} (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.)
When Shemesh assaults, other creatures you control get +2/+2 and gain trample until end of turn.

When Shepherd of Lonely Souls dies, you may return target creature card with mana value 4 or less from your graveyard to your hand.

Gestalt (When this or another creature enters under your control, you may merge it with the one in play, keeping counters and attachments. They become the permanent on top plus all abilities from under it.)
Trample
{1}, Discard Shifting Brute: Add one mana of any color. Scry 1.

When you unveil Shining Elementalist, creatures can't block this turn.

Flying
Instant and sorcery spells you cast cost {1} less to cast.
Whenever you cast your second spell each turn, draw a card.

{3}{U}{U}: Monstrosity 4. (If this creature isn't monstrous, put four +1/+1 counters on it and it becomes monstrous.)
When Shorecrash Octopus becomes monstrous, return target instant or sorcery card from your graveyard to your hand.

Flying, vigilance

This spell costs {2} less to cast for each face-down creature you control.
Flying

Vigilance
Whenever Sibling of All Elements attacks, it gains flying until end of turn if you control a creature with flying. The same is true for first strike, double strike, deathtouch, indestructible, lifelink, menace, and trample.

Desecrate (When this creature enters the battlefield, you may sacrifice an artifact or land.)
When Siltsplitter desecrates a permanent, each opponent sacrifices an artifact.

Trample
Whenever Silver-Dawn Ranger becomes the target of a spell, put a +1/+1 counter on each Warrior you control.

When Silverhorn Battlemaster enters the battlefield, put a +1/+1 counter on up to two target Warriors you control.
Whenever Silverhorn Battlemaster deals combat damage to a player, permutate. (You may remove a counter from a creature you control. If you do, put two +1/+1 counters on a different creature you control.)

When Silverhorn Tactician enters the battlefield, permutate. (You may remove a counter from a creature you control. If you do, put two +1/+1 counters on a different creature you control.)

Adorned — As long as Silverwork Champion is equipped and/or enchanted, it gets +2/+2 and has trample.

Whenever Sir Roger Wimbledon deals combat damage to a player, you may put an exiled creature card you own into your hand.

Whenever Sirif of the Lord's Legion attacks, you may put a lore counter on target Saga you control.
Whenever Sirif deals combat damage to a player, you may remove a lore counter from target Saga you control.

When Skelephant enters the battlefield, you may mill three cards.
Foresight — Whenever you draw your second card each turn, you may put target creature card from your graveyard on top of your library.

This spell can't be countered.
{U}: Exile Skulkling. Return it to the battlefield under its owner's control at the beginning of the next end step.
{1}{U}: Until end of turn, Skulkling gets +1/-1 ad can't be blocked.
{3}{U}: Draw a card. Create a 1/1 blue Rogue creature token.

Creatures with power less than Skull-Crowned Chief's power can't block.

Flying
At the beginning of your upkeep, sacrifice Skyward Dreamers unless you remove a counter from a permanent you control.

Improve {1}{B/R} ({1}{B/R}: 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.)
At the beginning of each player's combat, you may have that player create two goaded 1/1 red Goblin creature tokens with haste. Exile those tokens at end of combat. (Until your next turn, they attack each combat if able and attack a player other than you if able.)

Tribute 4 (As this creature enters the battlefield, an opponent of your choice may put four +1/+1 counters on it.)
When Slaughter enters the battlefield, if tribute was paid, destroy all other creatures. Otherwise, destroy all creatures you don't control.

Menagerie — {1}{G}: Slipsand Hornshell gains indestructible until end of turn. Tap it. Activate only if there are five or more creature types among creatures you control.

Deathtouch
When Slum Scrounger enters the battlefield, put up to two target creature cards in your graveyard on top of your library in any order.

When Slyten Analyst enters the battlefield, you may search your library for a card, then shuffle and put that card on top. If you do, you lose 2 life.