msem-instigator

Whenever a land you control enters, if you haven't had a land become a copy this way this turn, you may have that land enter as a copy of any nonland permanent on the battlefield.

[+1]: Each opponent loses 1 life for each card you've drawn this turn. Then you draw a card.
[–2]: Sun King's Shadow deals 2 damage to target creature or planeswalker and you gain 2 life. If that permanent was already dealt damage this turn, destroy it.

You may have Sun Yun enter as a copy of any creature on the battlefield, except her name is Sun Yun, Master of Man, she's legendary in addition to her other types, and she has “{2}{U}: Exile Sun Yun, then return her to the battlefield under her owner's control.”

If a creature entering the battlefield under your control causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.
{1}{U}, {T}: Exile another target creature. Return it to the battlefield under its owner's control at the beginning of the next end step.

{2}: Other creatures you control get +1/+0 until end of turn.
Whenever Sun-Crowned Flagship attacks, each attacking creature you control gains trample until end of turn.
Crew 7 (Tap any number of creatures you control with total power 7 or greater: This Vehicle becomes an artifact creature until end of turn.)

Vanguard — Whenever a creature you control attacks alone, you may cast a spell with mana value 3 or less from your hand without paying its mana cost.

Whenever you gain life for the first time each turn, draw a card.
{3}{G}{W}: You gain life equal to the greatest toughness among creatures you control.

When Sundering Arcanist enters, you may destroy target artifact or enchantment.
If you would draw a card, you may sacrifice a land and mill four cards instead. If you do, return Sundering Arcanist from your graveyard to your hand.

Whenever a land you control enters or a land card is put into your graveyard from anywhere, create a 0/1 green Plant creature token.
{3}{G}{G}: Put a +1/+1 counter on each other creature you control.

{1}, {T}: End the turn. Activate only during your turn.

Flying
As long as it's your turn, creatures you control get +3/+0 and have vigilance.
As long as it's not your turn, creatures you control get +0/+3 and have lifelink.

As Sunflower Fields enters, you may pay 3 life. If you don't, it enters tapped.
{T}: Add {R}, {G}, or {W}.

Return target creature to its owner's hand. Its controller loses 1 life.

Deathtouch
At the beginning of your end step, if you control no Sharks, create a 1/1 blue and black Demon Shark creature token with “This creature can't block” and “When this creature deals combat damage to a player, sacrifice it. If you do, draw a card.”

Sunken Homestead enters tapped.
{T}: Add {B}.
{2}{B}: Until end of turn, Sunken Homestead becomes a 2/2 Zombie creature with “When this creature dies, return it to the battlefield.” Activate only if you're horrific.

Primal {1}{W}{W} (During your turn, you may cast this spell for {1}{W}{W} instead of playing a land.)
Double strike
When Sunken Slasher enters, if you didn't play a land this turn, put a +1/+1 counter on it.

As Sunless Ridge enters, you may tap an untapped creature you control. If you don't, Sunless Ridge enters tapped.
{T}: Add {B} or {R}.

You gain life equal to the number of creatures you control.
Each opponent loses life equal to the number of creatures they control.
Destroy all creatures, then exile all graveyards.

Sunlit Fissure enters tapped.
{T}: Add {G} or {W}.
{2}{G}{W}: Until end of turn, Sunlit Fissure becomes a 3/5 green and white Elemental creature with with vigilance and “Whenever this creature attacks or blocks, torment yourself.” It's still a land. (To torment yourself, lose 3 life unless you discard a card or sacrifice a nonland permanent.)

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

Sunlit Ruins enters tapped unless you control a Swamp.
{T}: Add {G} or {W}.

Flying, haste
Assault {1}{R} (Whenever this attacks, if it has no +1/+1 counters on it, you may pay its assault cost to put a +1/+1 counter on it.)
Whenever one or more +1/+1 counters are put on a creature you control, you may return Sunnula's Firebird from your graveyard to your hand.

Equipped creature has “{T}: This creature deals damage equal to its power to any target.”
Equip {4}

Sunrazed Ruins enters tapped.
{T}: Add {W}.
{2/W}{2/W}: Sunrazed Ruins becomes a 2/3 white Elemental creature with lifelink until end of turn. It's still a land.

Sunrise Bluffs enters tapped.
{T}: Add {R}.
You may untap Sunrise Bluffs during each other player's untap step. Whenever you do, you lose 1 life.