msem-instigator

Reveal the top seven cards of your library. Starting with you, each player chooses a nonland card from among them that hasn't been chosen this way. Put the chosen cards into your hand and the rest on the bottom of your library in a random order.

First strike
Whenever a creature you control with power 4 or greater attacks, you may pay {1}{R}. When you do, target creature gets +3/+2 and gains trample until end of turn.

Choose one —
• Untap each creature you control.
• Harmonize twice. (To harmonize, trigger up to one harmony of a permanent you control.)

Fleshweaver's Domain enters tapped.
{T}: Add {G}.

Return target creature you control and target creature you don't control to their owners' hands.

Deathtouch
{2}{G}: Transform Adderblade Exterminator. Activate only if it's attacking.

Flying
Other Dragons you control have haste.
{R}: Dragons you control get +1/+0 until end of turn.

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
{3}{U}: Target creature gains slipstream until end of turn.

{2}, {T}: Put a +1/+1 counter on target creature you control.
{2}, {T}, Sacrifice Inspiring Effigy: Put a +1/+1 counter on each creature you control.

{T}, Sacrifice an artifact: Add {R}{R}{R}.

Sire of the Shapeless costs {3} less to cast as long as you control three or more creatures.
Trample, haste
{G}, Reveal Sire of the Shapeless from your hand: Create a 1/1 colorless Human creature token. Shuffle Sire of the Shapeless into your library. Activate only as a sorcery.

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.)
Other creatures you control have base power and toughness equal to this creature's base power and toughness.

When Ethersworn Elite enters, you gain 2 life and create two 1/1 blue Thopter artifact creature tokens with flying.
Cycling {2} ({2}, Discard this card: Draw a card.)

Uncharted Haven enters tapped.
As Uncharted Haven enters, choose a color.
{T}: Add one mana of the chosen color.

Puzzlebox (Begin the game with this and another card you own from outside the game in the command zone, locked. That card is face down until you unlock this.)
{5}: Unlock Key to the Nexus. If {W}{U}{B}{R}{G} was spent to activate this ability, you may cast the revealed card without paying its mana cost. Otherwise, put that card on top of your library.

Double strike
Improve {1}{R/W} ({1}{R/W}: 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 combat on your turn, if you control three or more embattled creatures, you may search your library for an artifact, enchantment, or Angel card, reveal it, put it into your hand, then shuffle.

Whenever a permanent you control becomes tapped, Storm Servant gets +1/+1 until end of turn.

Flying, ward {2}
Whenever Realm Crossers deals combat damage to a player, create a blue enchantment token named Tambo with “At the beginning of your upkeep, draw a card if you control a Scout.”

Whenever a permanent with one or more counters on it is put into your graveyard from the battlefield, it deals that much damage to any target and you gain that much life.

Lionize {1}{B} ({1}{B}, Exile this card from your hand: Put a +1/+1 counter on target creature and it gains the following ability until end of turn. You may cast this card on a later turn from exile.)
Deathtouch

{1}, Sacrifice Martyr of the Work: Purge. (Exile two cards that share a type from graveyards. If you do, draw a card.)

{B}, {T}, Sacrifice Planar Eulogist: Aetherize target creature card in a graveyard. (To aetherize, create a token that's a copy of it, then exile that token.)
{6}{B}: Aetherize target creature card in a graveyard.

Artifacts and lands enter tapped.

Gain control of target creature with power 2 or less until end of turn. Untap that creature. It gains haste until end of turn.

When Scintillating Tome enters, choose a nonbasic card name.
{T}: Scry 1, then you may reveal the top card of your library. If a card with the chosen name is revealed this way, put it into your hand.