msem-instigator

If one or more counters would be put on a permanent you control, you may have that many counters plus one or that many counters minus one put on that permanent instead.

{1}, {T}, Move a -1/-1 counter from another creature onto Harried Apothecary: Each opponent loses 1 life and you gain that much life.

As an additional cost to cast this spell, sacrifice a permanent.
When Harriet, Liberated Wildborn enters, you may remove all counters from target permanent.

Target player discards two cards and loses 2 life. Scry 2. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom of your library and the rest on top in any order.)

Whenever you cast a black spell, you may exile target creature. Return that card to the battlefield under its owner's control at the beginning of the next end step.
Whenever you cast a red spell, you may have Haunted Sunseeker deal 1 damage to each creature.

{T}, Sacrifice Hazy Lagoon: Search your library for a Plains or Island card and put it onto the battlefield tapped, then shuffle.

Menace
When Heart of the Deadwood enters, destroy up to one target creature, then put up to one target creature card from a graveyard onto the battlefield under your control.

Enchant creature
Prevent all damage that would be dealt by enchanted creature.
{R}, Sacrifice Heat of Day: It deals 2 damage to enchanted creature.

When Heedless Lovers enters, you may return target Citizen card from your graveyard to your hand.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

[+2]: Until end of turn, Helene Trant becomes a 4/4 Human Warrior creature with hexproof and trample that's still a planeswalker. Prevent all damage that would be dealt to her this turn.
[–2]: Draw two cards.
[–4]: You get an emblem with “Whenever one or more creatures you control deal combat damage to a player, draw a card.”

{1}{U}, {T}: Reveal the top card of your library. If it doesn't share a color with Heretical Seer, put it into your hand.

For each color among nontoken permanents you control, add one mana of that color.

Whenever a player casts a spell, that player reveals cards from the top of their library until they reveal two land cards, then puts all cards revealed this way into their graveyard.

{1}{U}, Tap an untapped Noble you control: Hired Blades gets +2/+1 until end of turn and can't be blocked this turn.

Trample
Hollow Survivor's power and toughness are each equal to the number of cards in your hand.
Whenever Hollow Survivor deals combat damage to a player, draw a card.

While an opponent is choosing targets as part of casting a spell they control or activating an ability they control, that player must choose at least one Flagbearer on the battlefield if able.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Flying
Whenever a Harpy you control becomes the target of a spell, scry 1.

Flying
When Horned Spy enters, look at target player's hand.

Search your library for an enchantment card, reveal it, put it into your hand, then shuffle.

You may put a creature card from your hand onto the battlefield. That creature gains haste. Sacrifice that creature at the beginning of the next end step.

Whenever Impetuous Impetus deals combat damage to a player, you may sacrifice a land. If you do, Impetuous Impetus deals 3 damage to that player.

Haste
When Inciting Bard enters, other creatures you control get +1/+0 and gain haste until end of turn.

At the beginning of your end step, shuffle your hand and graveyard into your library, then draw seven cards.

When Influential Wildborn enters, proliferate. (Choose any number of permanents and/or players with counters on them, then give each another counter of each kind already there.)
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)