msem-instigator

When Seishin Tidekeeper enters, create a 2/2 colorless Spirit creature token.
Colorless creatures you control have flying.

Equipped creature gets +1/+0 for each colorless creature you control.
Equip {1}

Equipped creatures you control get +1/+1.
You may activate equip abilities any time you could cast an instant.
Equip {2}

Senaturian Legion gets +1/+1 for each other creature on the battlefield named Senaturian Legion.
A deck can have any number of cards named Senaturian Legion.

Untap all permanents you control during each other player's untap step.

Flying, vigilance
Whenever Sepulchral Guide attacks, prevent all combat damage that would be dealt to another target creature you control this turn. If that creature has two or more counters on it, untap it.

Enchant creature
Enchanted creature doesn't untap during its controller's untap step.
{2}{U}: Return Sequester to its owner's hand.

Prevent all damage target spell or permanent would deal this turn. You gain life equal to the damage prevented this way.

Target creature gets -2/-2 until end of turn. When that creature dies this turn, its controller loses 2 life or gets a poison counter.

Noncreature spells your opponents cast cost {1} more to cast.

Destroy all creatures.

Flash

Once each turn, when another creature you control enters, you may search your library for a card with the same name as that creature, reveal it, put it into your hand, then shuffle.

Destroy target creature. If an opponent lost life this turn, that creature's controller mills five cards.

Shadow Courier can't be blocked.

Your opponents play with their hands revealed.

Shadowcleft Hideout enters tapped.
{T}: Add {B}.
{T}, Pay 2 life, Sacrifice Shadowcleft Hideout: Draw a card.

When Shadowstrider dies, create a 2/2 colorless Spirit creature token.

Prowess
Each instant and sorcery card with mana value 3 or less in your hand has inscribe. The inscribe cost is equal to its mana cost increased by {1}{U/R}. (Pay that card's mana cost increased by {1}{U/R}: Exile that card from your hand inscribed on a creature you control. Whenever that creature attacks, its controller may cast a copy of the inscribed card without paying its mana cost. Inscribe only as a sorcery.)

As long as Shambling Morass is on the battlefield or in your graveyard, it's a land in addition to its other types.
When Shambling Morass dies, you may pay {1}. If you do, you draw a card and you lose 1 life.

Menace, lifelink
Whenever a creature enters under an opponent's control, you may have that player lose 1 life.

Create a colorless Equipment artifact token with “Equipped creature gets +1/+1” and equip {1}. You may attach it to a creature you control.
Inscribe {3}{R} ({3}{R}: Exile this card from your hand inscribed on a creature you control. Whenever that creature attacks, its controller may cast a copy of the inscribed card without paying its mana cost. Inscribe only as a sorcery.)

As Shardstone Rift enters, you may pay 2 life. If you don't, Shardstone Rift enters tapped.
{T}, Sacrifice Shardstone Rift: Search your library for a Swamp or Mountain card, put it onto the battlefield, then shuffle.

Discard a land card: Draw a card. Shardstorm Elemental gets +1/+0 and gains flying until end of turn. Activate only once each turn.

Trample
Improve {1}{R} ({1}{R}: Put a +1/+1 counter on this creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)
Embattled creatures you control get +2/+0. (A creature is embattled if it has a counter on it or has a permanent you control attached to it.)