msem-instigator

Whenever a creature enters, each opponent loses 1 life.

Whenever you gain life, put a +1/+1 counter on Listless Maneli.
Surpass {5}{W} ({5}{W}: Transform this creature. This costs {1} less to activate for each counter on it. Activate only as a sorcery.)

Create a 3/2 green Horror creature token.
Reconstruct {4}{G} (You may cast this from your graveyard for its reconstruct cost reduced by the mana value of a permanent you sacrifice as you cast it this way. Then exile this.)

Gain control of target artifact or creature until end of turn, then untap it. It gains haste until end of turn. You may spend mana as though it were mana of any type to pay the costs of its abilities this turn.

{6}: Until the next time this ability resolves, and as long as Helm of the Infinite and target creature you control are on the battlefield, each other creature is a copy of that creature, and effects that would cause permanents to become creatures cause them to become copies of that creature instead.

When Speed Reader enters, harmonize. (Trigger up to one harmony of a permanent you control.)
Harmony — Add {R}{R}.

Distorted (This creature can be blocked by tapped creatures but not untapped creatures.)
Oslyd Heretic gets +1/+1 as long as you control no other creatures.

Whenever another creature you control dies, each opponent loses 1 life. If it had two or more counters on it, draw a card.
{1}{U}{B}: Put a -1/-1 counter on target creature you control and target creature an opponent controls. Activate only as a sorcery.

Whenever a player casts an instant or sorcery spell that targets only one target or activates an ability that targets only one target, copy that spell or ability for each other target it could target. Each copy targets a different one of those targets. (A spell or ability can't target itself.)

Ominous Lightning deals 3 damage to target creature. Scry 2.

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
Whenever Conchhorn Shinygrabber attacks, you may pay {1}. If you do, create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)
{W}{U}{B}{R}{G}: Conchhorn Shinygrabber gets +3/+3 and gains lifelink until end of turn.

Trample, hexproof
When Maw of a Thousand Worlds enters, distribute X +1/+1 counters among creatures you control, where X is the number of differently named lands you control.
When Maw of a Thousand Worlds dies, you may remove any number of counters from among permanents you control. For each counter removed this way, draw a card.

Lionize {2}{B} ({2}{B}, Exile this card from your hand: Put a +1/+1 counter on target creature and it gains the following ability until end of turn. You may cast this card on a later turn from exile.)
Lifelink

Rouse 1. Target permanent gains first strike until end of turn if it's a creature. (Put a +1/+1 counter on a permanent you control. If it isn't a creature, tap it and it becomes a 0/0 creature in addition to its other types.)

Griffin Country enters with a feather counter on it.
Creatures with flying you control get +1/+1.
{U}, Remove a feather counter from Griffin Country: Put a flying counter on target creature you control.
{2}{U}, Remove a feather counter from Griffin Country: Search your library for a creature card with flying, reveal it, put it into your hand, then shuffle.

Enchant opponent
Enchanted player plays with the top card of their library revealed.
You may cast the top card of enchanted player's library, and you may spend mana as though it were mana of any type to cast it.

Damage can't be prevented.
At the beginning of your upkeep, Bomb Juggler deals 3 damage to target player chosen at random.

Target creature gets +2/+0 and gains flying and first strike until end of turn.

Flying, haste
Whenever Shimmering Dragon attacks, for each creature you control, create a tapped and attacking token that's a copy of that creature. Exile the tokens at the beginning of the end step.

{T}: Add {C}.
{1}, Discard Imperial Port: Search your library for a basic land card, reveal it, and put it into your hand. Then shuffle.

Menace
Whenever you cast an instant or sorcery spell, create a 2/2 black Zombie creature token. This ability triggers only once each turn.

Whenever Masha's Vanguard deals damage to a player, you may put a creature card with mana value X or less from your hand onto the battlefield, where X is the amount of damage dealt this way.

When Rotting Greatwurm dies, put three +1/+1 counters on target creature you control.
Fleeting {2}{G} (You may cast this spell for its fleeting cost. If you do, sacrifice it at the beginning of the next end step.)

When Spinegraft Disabler enters, exile target creature until Spinegraft Disabler leaves the battlefield.

Flash
{1}{W}: Exile target creature that dealt damage to you this turn until The Shield leaves the battlefield.