msem-instigator

Flash
When Decisive Arcanist enters, you may cast target modal instant or sorcery card in your graveyard. Exile that card instead of putting it into your graveyard as it resolves.

Whenever another creature you control enters, you may change Declan, Wayward Squire's base power and toughness to that creature's power and toughness until end of turn.

Indestructible (Damage and effects that say “destroy” don't destroy this creature.)
Whenever Declare, the Mother Bear deals combat damage to a player, put a +1/+1 counter on it.

Counter target creature spell, planeswalker spell, or activated ability.

Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)
Whenever a player activates an ability of an artifact, creature, or land, if it isn't a mana ability, Dedicated Weaponsmith deals 2 damage to that player.

Deepdrinker's Domain enters tapped.
{T}: Add {U}.

Deeplife Cavern enters tapped unless you control a Forest.
{T}: Add {U} or {B}.

Menace
Creatures you control get +1/+0 as long as you've foretold a card this turn.
Creatures you control get +1/+0 as long as you've cast a foretold spell this turn.

Target opponent reveals their hand. You choose a nonland card from it. That player discards that card.
Create a Function token with “Draw a card if a player discarded a card this turn.” (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

Destroy target creature or planeswalker.
Compose (Then if you cast this from your hand, exile it and create a Saga token with “r3—You may cast a copy of this card from exile without paying its mana cost.”)

As long as it's your turn, Defect 37 is a 7/7 Vehicle artifact with crew 2.
[+1]: Creatures and Vehicles you control get +1/+1 until end of turn.
[–1]: Put target permanent into its owner's library, third from the top. If Defect 37 is on the battlefield, return her to her owner's hand.
[–6]: Until end of turn, each noncreature, nonland permanent you control becomes a creature in addition to its other types with base power and toughness each equal to their mana value or base power, whichever is greater.

{T}: Add {C}.
{3}{R}: Until end of turn, Defect's Precinct becomes a 3/3 creature. It's still a land. It has trample if {G} was spent to activate this ability, has vigilance if {W} was spent, and has hexproof if {U} was spent.

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.)
Whenever you draw a permanent card from the archived library, you may have Defect's Study become a copy of it until end of turn.

Whenever you cast a spell, if it shared a color with the last spell you cast this turn, put two +1/+1 counters on Defected Android.

Spells can't be cast from libraries.
If a nonland permanent would enter from a library, exile it instead.

Flying, vigilance
Whenever you attack, if you've cast a spell from a graveyard this turn, you may pay {1}{W}. If you do, put Defender of Carü Mapu from your graveyard onto the battlefield. It's attacking.

This spell can't be countered.
You can't lose the game this turn and your opponents can't win the game this turn. Until end of turn, damage that would reduce your life total to less than 1 reduces it to 1 instead.

As an additional cost to cast this spell, discard a nonland card.
Target player reveals their hand. You choose a nonland card from it. That player discards that card.

Search target opponent's library for a card and exile it, then do the same for their hand and graveyard. That player shuffles. You may cast spells exiled this way for as long as they remain exiled, and you may spend mana as though it were mana of any color to do so.

Flash
When Dehmi, Origin Seeker enters, counter target spell an opponent controls unless that spell's controller has you create X 1/1 red Elemental creature tokens, where X is that spell's mana value.

When Deliver from Dilapidation enters, you may sacrifice any number of enchantments. Whenever you sacrifice an enchantment this way, destroy target creature.
At the beginning of your upkeep, return target enchantment card with mana value 5 or less from your graveyard to the battlefield.

Creatures you control get +1/+1 for each noncreature spell you've cast this turn.
When Deliverance Branch enters, create three 1/1 white Cleric creature tokens with lifelink.

Repeat the following process X times. Reveal the top two cards of your library. Put one of them into your hand and the other into your graveyard.

At the beginning of your upkeep, choose a creature. Its controller may sacrifice it. If that player doesn't, you gain life equal to its power.

When Demented Brainiac enters and at the beginning of your upkeep, each opponent mills two cards.
{U}, Sacrifice Demented Brainiac: Exile each opponent's graveyard. Until end of turn, you may cast instant and sorcery spells exiled this way, and you may spend mana as though it were mana of any color to cast them.