msem-instigator

Until end of turn, target creature you control gains double strike and trample. Sacrifice it at the beginning of the next end step.
Draw a card.

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.

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

Reach, ward {3}

Soldiercycling {1}{W}, Wizardcycling {1}{U}, Zombiecycling {1}{B}, Warriorcycling {1}{R}, Elfcycling {1}{G} ({1}{G}, Discard this card: Search your library for an Elf card, reveal it, and put it into your hand, then shuffle.)
Sentinel of Latter Days is every creature type as long as it's in your library.

Sentinel of the Highlands has hexproof as long as it's embattled. (A creature is embattled if it has a counter on it or has a permanent you control attached to it.)

Equipped creature has vigilance and reach.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

{T}: Add {C}.
{T}, Reappropriate: Add {U} or {B}. (Exile exactly two cards from your hand and/or graveyard.)

Sera of Coppercove attacks each combat if able.
Whenever Sera of Coppercove attacks, it fights target creature you don't control.
{1}{R}{G}: Sera of Coppercove gets +3/+3 until end of turn.

Equipped creature gets +2/+0 and can't block.
Equip {1}

Serene Chapel enters tapped unless you control a basic Plains.
{T}: Add {W}.
{1}{W}{W}: Until end of turn, Serene Chapel becomes a 2/1 white Spirit Cleric creature with flying and “Whenever this creature attacks, you may exile target card from a graveyard.” It's still a land.

Mill four cards, then return a creature or enchantment card from your graveyard to you hand. You gain 3 life.

When Serene Initiate enters, rouse 1. (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.)
{3}{G}{G}: Creatures you control get +2/+2 and gain trample until end of turn.

{T}: Add {G} or {U}. You lose 1 life unless you have less life than an opponent.

Choose one —
• Return target permanent card from your graveyard to your hand.
• Destroy target artifact or enchantment.

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

Equipped creature gets +1/+1 and has deathtouch.
{1}: Serpent Staff becomes a 1/1 green Snake creature with deathtouch and loses all other abilities until end of turn.
Equip {3}

Enspirit (As you cast this spell, you may exile a nonenchantment creature you control until this leaves the battlefield or fails to resolve. Reduce this spell's cost by the exiled card's mana value.)
{T}: Add {G}{G}.

Serpentine Woods enters tapped.
{T}: Add {B} or {G}.
{2}{B}{G}, {T}, Sacrifice Serpentine Woods: Draw a card.

When Servant of Armageddon dies, destroy all creatures.

When Servant of Precursors enters, you gain 4 life and draw a card.

Menace
Servitor Vanguard gets +X/+X, where X is the number of other artifacts you control.

Equipped creature gets +2/+2 and has ward {2} and “Whenever this creature attacks, draw a card, then you may put a land card from your hand onto the battlefield.”
Equip {2}

Heroic — Whenever you cast a spell that targets Setessan Avenger, create a 1/1 green Nymph Dryad enchantment creature token with “{T}: Add {G}.”
Whenever Setessan Avenger deals combat damage to a player, untap all lands and Dryads you control.

{T}: Add {C}.
{5}{R}{G}, {T}: Transform Settled Satrapy.