msem-instigator

Equipped creature gets +2/+0.
Whenever a creature blocks equipped creature, you may sacrifice Elderbane Rifle. If you do, destroy that creature.
Equip {2}

At the beginning of each combat, you may have Elderin, Crystalline Crusader become a copy of another target creature you control with mana value 3 or less until end of turn, except its name is still Elderin, Crystalline Crusader, it's still 3/3, still legendary, and it's an artifact in addition to its other types.
{W}{U}{B}{R}{G}: Elderin gets +3/+3 until end of turn.

When Elderthrone Castellan enters, you may search your library for a Plains card, reveal it, put it into your hand, then shuffle.

{T}: Add one mana of any color.
{T}, Sacrifice Elderthrone Shard: Draw a card.

{0}: Until end of turn, Eldritch Egg becomes a copy of target permanent card in a graveyard with mana value 6 or less except it's an artifact. Activate only once each turn. (It has no other card types.)

You may reveal an Avatar or planeswalker card you own from outside the game and put it into your hand.

Primal {U} (During your turn, you may cast this spell for {U} instead of playing a land.)
Counter target spell.

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever you cast a noncreature spell, you may have Elegant Fireslinger deal 1 damage to target creature.

Elemental Envelopment enters with X +1/+1 counters on it.
When Elemental Envelopment enters, if you controlled a green legendary creature or planeswalker as you cast it, search your library for any number of Elemental creature cards with total mana value X or less, where X is Elemental Envelopment's power, put them onto the battlefield, then shuffle.

When Elemental Loremaster enters, return an instant or sorcery card at random from your graveyard to your hand.

Flash
Creatures you control that have entered this turn get +1/+1 and have haste and first strike.

[+1]: Create a tapped colorless Bullet artifact token with “{T}, Sacrifice this artifact: It deals 1 damage to any target.”
[–1]: Exile target creature or planeswalker that was dealt damage this turn.
[–7]: You get an emblem with “At the beginning of each end step, you may draw X cards, where X is the amount of life your opponents lost this turn.”

At the beginning of combat on your turn, creatures you control gain your choice of trample, menace, haste, or +1/+0 until end of turn.

[+1]: Create a 1/1 white Warrior creature token.
[–1]: Another target permanent you control gains indestructible until your next turn.
[–8]: You get an emblem with “Creatures you control get +2/+2.” and “Prevent all damage that would be dealt to attacking creatures you control.”

Flash
{U}, Put Elusive Hunter into its owner's library second from the top: Counter up to one target spell unless its controller pays {2}.

Flash
When Elusive Illusionist enters, target attacking creature gets -2/-0 until end of turn.

{1}{U}: Exile Elusive Monkey. Return it to the battlefield under its owner's control at the beginning of the next end step.

When Ema, the Traveler enters, reveal the top five cards of your library. Put any number of legendary cards revealed this way into your hand and the rest on the bottom of your library in any order.
{2}{B}: Another target legendary permanent gains indestructible until end of turn.

Prowess, haste
When Embercore Grazer enters, add {R}{R}{R}. Spend this mana only to cast instant and/or sorcery spells.

When Embrace Samang enters, put a charge counter on it for each color among permanents you control.
At the beginning of your first main phase, remove a charge counter from Embrace Samang. If you do, draw a card, then add one mana of any color.

Each creature has haste and “At the beginning of combat on your turn, choose an opponent at random. This creature attacks that player this combat if able.”

When Embrace the Veil enters, you may exile target nonland permanent you don't control until Embrace the Veil leaves the battlefield.
Whenever you cast a spell with mana value 5 or greater, you may put a card exiled with Embrace the Veil into its owner's graveyard and return Embrace the Veil to its owner's hand.

Chosen one ({W}{U}{B}{R}{G}: Transform this permanent.)
At the beginning of combat on your turn, create a 1/1 red Warrior creature token with haste. That token attacks this combat if able.

Choose one —
• Create two 1/1 blue Tentacle creature tokens.
• Untap target creature. It gets +2/+4 until end of turn.