msem-instigator

{T}: Add {C}.
{T}, Pay 1 life: Add {U}.
{U}, {T}: Add one mana of any color.

{T}: Add {C}.
{T}, Pay 1 life: Add {R}.
{R}, {T}: Add one mana of any color.

{T}: Add {C}.
{3}, {T}: Aetherize target permanent you control. Activate only as a sorcery. (To aetherize, create a token that's a copy of it, then exile that token.)

When you unveil Starlight Guardian, you may put target card from your graveyard on top of your library.
If a card would be put into an opponent's graveyard from anywhere, exile that card instead.

{T}: Add {C}.
{2}, Pay 2 life: Starved Oasis becomes a 4/2 Elemental creature until end of turn. It's still a land.

Until end of turn, if a source you don't control would deal damage to you or cause you to lose life, mill that many cards instead.

({T}: Add {U} or {R}.)
Steamlit Peaks enters tapped.
{1}, {T}: Add {U}{U} or {R}{R}.

(Transform this if it's not attached to a creature. Pay {2}{U} as a sorcery to unattach it.)
Enchant creature you control
Steed of the Loch's rider gets +2/+1.
Whenever Steed of the Loch's rider attacks, you may tap target creature an opponent controls.

Steelborn Apprentice gets +1/+1 as long as you control an Equipment.

Flash
Advance {3}{W} (Cast this for {3}{W} to advance it as it enters. {3}{W}: Advance this as a sorcery.)
Whenever Steelwoven Soldier advances, it gets +2/+2 until end of turn.

Choose one —
• Search your library for a basic land card, reveal it, put it into your hand, then shuffle.
• Create a tapped token that's a copy of target token you control.

({T}: Add {W} or {U}.)
Still Waters enters tapped unless you control two or more basic lands.

Enchant creature
When Sting of the Manticore enters, scry 2.
Enchanted creature gets +1/+0 and has deathtouch.

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)

Whenever you cast a spell that doesn't share a color with Stinging Hunter, each opponent loses 1 life.

Choose a nonland card type. Target player reveals their hand. You choose a card of the chosen type from it. That player discards that card.

{1}, {T}, Sacrifice Stolen Strain: Target creature gains lifelink until end of tun.
{1}, {T}, Sacrifice Stolen Strain: Target creature gains winnow until end of turn. (Damage dealt to it also causes its controller to lose that much life.)

Look at target opponent's hand. You may cast a card from that player's hand or graveyard, and you may spend mana as though it were of any type to cast that card. If you cast a card from that player's hand this way, that player draws a card.

Creature spells cost {1} more to cast.
At the beginning of your upkeep, put a decay counter on Stonewood Sanctuary. Then if it has three or more decay counters on it, sacrifice it.

At the beginning of your upkeep, if Stonework Infantry is on the battlefield, each player returns all cards named Stonework Infantry from their graveyard to the battlefield.

Colossal 3—{4}{R} (You may cast this for its colossal cost to have it enter with three +1/+1 counters; or pay {4}{R} as a sorcery: Put three +1/+1 counters on it if it has none.)
When Storm-Eye Salamander's colossal ability puts one or more counters on it, exile the top three cards of your library. Until the end of your next turn, you may play one of those cards.

{T}: Add {C}.
{T}, Exile two cards from your graveyard: Add {U} or {R}.

Stormcharged Pyre enters tapped unless you have two or more opponents.
{T}: Add {U} or {R}.

Prowess, haste

Whenever one or more creatures you control deal combat damage to a player, exile a nonland card from that player's graveyard. Copy it. You may cast the copy. (You still pay its costs, including color. Copies of permanents enter as tokens.)