msem-instigator

Equipped creature gets +1/+0.
Whenever equipped creature attacks, you may draw a card then discard a card.
Equip {2}

Counter target instant or sorcery spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Flying
When Arcanum Owl enters the battlefield, you may return target instant or sorcery card from your graveyard to your hand.

Lifelink
Arcblade Enforcers gets +1/+1 as long as you control an enchantment.

Gain control of target artifact or creature until end of turn. Untap it. It gains haste until end of turn.

When Archaeomancer enters the battlefield, return target instant or sorcery card from your graveyard to your hand.

Whenever you cast a noncreature spell, Architect of Calamity deals 2 damage to each opponent.

When Archivist Heretic enters the battlefield, you lose 1 life, then investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Flying, prowess

Flying, vigilance

Flying
Whenever Archon of Inspiration attacks, add three mana in any combination of colors at the beginning of your next postcombat main phase.

Flying, trample

Flying
{1}: Archon of Supremacy gets +1/-1 until end of turn.

Flying, menace

Exile up to three target creatures you control, then return those cards to the battlefield under your control tapped.

When Arcor-Staff Adherent enters the battlefield, you may remove all -1/-1 counters from target creature.

Attacking creatures you control get +1/+0 until end of turn.
Draw a card.

Wanderlust — When Ardent Explorers enters the battlefield, if you control four or more differently named lands, create a 1/1 Scout creature token that's all colors. That token gains haste until end of turn.

Kicker {1}{R} (You may pay an additional {1}{R} as you cast this spell.)
Attacking creatures get +2/+0 until end of turn. Those creatures also gain first strike until end of turn if this spell was kicked.

Arid Causeway enters the battlefield tapped unless you control another Desert.
{T}: Add {R} or {W}.

When Aridland Camaar enters the battlefield, create a 1/1 white Bird creature token with flying.

If a creature would leave the battlefield this turn, exile it instead.
Spell mastery — If there are two or more instant and/or sorcery cards in your graveyard, target player sacrifices a creature.

When Arisen Haploc enters the battlefield, return target creature card from a graveyard to its owner's hand.
Revive {5}{B}{B} ({5}{B}{B}, 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 Arisen Helix attacks, scry 2.
If Arisen Helix would die, exile it instead.

Whenever you cast a noncreature spell, each opponent loses 1 life.
{4}, Exile Arisen Psion from your graveyard: Draw a card.