msem-instigator

(Transform this if it's not attached to a creature. Pay {2}{B}{B} as a sorcery to unattach it.)
Enchant creature you control
Belmord Blood-Coach's rider gets +3/+3 and has deathtouch.
Whenever Belmord Blood-Coach's rider attacks, you may return target creature card with mana value less than its rider's power from your graveyard to the battlefield tapped.

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.)
Double strike
If this creature would deal noncombat damage, it deals double that damage instead.

Instant and sorcery spells you cast cost {1} less to cast.
{U}, {T}, Exile three instant and/or sorcery cards from your graveyard: Draw a card.

Flying
This spell can't be countered.
When Frostbreath Dragon enters, tap target creature. It doesn't untap during its controller's next untap step.
Whenever Frostbreath Dragon becomes the target of a spell or ability, counter it unless its controller pays {2} and discards a card.

Choose one —
• Festival Sabotage deals 2 damage to any target.
• Audition for red. (Create a 1/1 Construct Actor creature token, a Warrior Role giving 3/2 and trample, or a Wizard Role giving 2/2 and prowess. Roles replace older ones.)

Menace
Stampede — Whenever Maelstrom Slicer and a creature with greater power attack, exile the top three cards of your library. You may play those cards until end of turn.

Flying, vigilance

Enchant creature
Enchanted creature gets +1/+3 and has flying.

When Neo-Soul Naturalist enters, exile up to one target artifact or enchantment. Its controller conjures a card named Data-Point into their hand. (It's a sorcery that costs {2} with “Draw a card.”)

When Warden of the Dead enters, you draw a card and you lose 1 life.
When Warden of the Dead dies, conjure three cards named Warden of the Dead and shuffle them into your main library. For the rest of the game, you may cast spells named Warden of the Dead without paying their mana costs.

{T}: Add {G}. When that mana is used to cast a spell with mana value 5 or greater, you may untap Performer of Growth and transform it.

When Glimpse in the Static enters, exile target creature an opponent controls until Glimpse in the Static leaves the battlefield.
At the beginning of your upkeep, target player creates a token that's a copy of the exiled card, then exiles that token.

Archive 5 (As this enters, shuffle the top five cards of your main library into a new face up library. Sacrifice this after the archived library is empty.)
Encylopetia's power and toughness are each equal to the number of cards in the archived library.
At the beginning of your upkeep, exile a card from the archived library at random. You may play it this turn.

Enchant creature you control
When Flamespeaker's Craft enters, it deals 2 damage to any target.
Enchanted creature has “{T}, Discard a card: Draw a card.”

Creatures you control get +1/+1 until end of turn. You gain 3 life.
Memento {4}{W}{W} (You may cast this from your graveyard for {4}{W}{W}. If you do, put it onto the battlefield transformed after it resolves. Exile it if it would leave the battlefield or not resolve.)

Enchant creature
As Legacy of Siltbottom enters, choose a creature type.
Enchanted creature gets +3/+3 and is the chosen type in addition to its other types.

Whenever an attacking creature you or a teammate controls dies, Burned Bounty deals damage equal to that creature's power to each opponent.

Discard any number of cards, then sacrifice any number of artifacts. Draw X cards, where X is one plus the number of cards discarded and artifacts sacrificed this way.

When Fidelity of the Pure dies, create a 1/1 green and white Elk Spirit creature token.
Revive {2}{W} ({2}{W}, Exile this card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

Whenever you cast a spell with mana value 4 or greater, catalyze. (The next spell you cast this turn costs {1} less to cast.)

Other Rogues you control have menace.
{2}{U}: Target blocking creature gets -1/-0 until end of turn.

{T}: Add {C}.
{4}, {T}: Create a 0/1 white Goat creature token.
{T}, Sacrifice X Goats: Add X mana of any one color. You gain X life.

For each creature token you control, create a token that's a copy of that creature.

This spell can't be countered.
Whenever another nontoken creature you control dies, return it to its owner's hand at the beginning of the next end step.
{6}{G}: Transform Krendel of Kessig. Activate only if it's attacking.