msem-instigator

When Seikatsu Warleader enters, if it's not a token, create a token that's a copy of target creature token you control.

{T}: Add {C}.
{7}, {T}: Create a 2/2 colorless Spirit creature token.

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

When Seishin Smokeshaper enters, create a 2/2 colorless Spirit creature token.
Whenever you cast a noncreature spell, colorless creatures you control get +1/+1 until end of turn.

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}

Destroy target land. Add {R}{R}.

Seismic Strike deals damage to target creature equal to the number of Mountains you control.

Another target player reveals their hand. You may choose an instant or sorcery card from it and cast it without paying its mana cost.
Fuse (You may cast one or both halves of this card from your hand.)

Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)
Whenever a +1/+1 counter is put on Sejiri Skyhunter, it gains flying until end of turn.

Create a 1/1 colorless Construct artifact creature token. If you control an artifact, create two of those tokens instead.

Enchant creature
Enchanted creature gets +1/+1 and has lifelink.

{3}: Sellsword Contraption becomes the creature type of your choice until end of turn.

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.

Return target non-Horror creature to its owner's hand. Scry 1.

Return up to one target creature you control and up to one target creature you don't control to their owners' hands.

When Sending Stones enters, harmonize twice. (To harmonize, trigger up to one harmony of a permanent you control.)
If you would harmonize, you may trigger a harmony of a permanent card in your graveyard instead.

Choose one —
• Target permanent gains protection from instants and sorceries until end of turn.
• You gain 3 life.
• Draw a card.

Destroy target creature. Trigger a death knell of a permanent you control.

You may put cards with Adventures that permanents you control explore into your hand as though they were lands. (You won't get the counter if you do.)
At the beginning of each end step, if you cast an Adventure spell or a permanent you controlled explored this turn, create a 1/1 green Scout creature token.

Target player discards two cards. If a creature you control died this turn, that player loses 2 life.

{2/U}, {T}: Target creature gets -4/-0 until end of turn.

Choose one —
• Untap each creature you control.
• Harmonize twice. (To harmonize, trigger up to one harmony of a permanent you control.)

When Sentient Contraption enters, create a 1/1 colorless Thopter artifact creature token with flying.

Target noncreature artifact you control becomes a 0/0 artifact creature. Put three +1/+1 counters on it.