msem-instigator

Scry 2, then reveal the top card of your library. If it's a basic land card, put it onto the battlefield tapped. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom of your library and the rest on top in any order.)

When Symbiotic Sprout dies, create two 1/1 green Saproling creature tokens.

(As this Discovery enters and after your draw step, add a progress counter. Stop after you've discovered.)
Archive 6 (As this enters, shuffle the top six cards of your main library into a new face up library. Sacrifice this after the archived library is empty.)
Draw a card from each of your libraries.
discover — When you draw the last card from the archived library, create a 4/4 blue Sphinx Wizard creature token with flying.

Whenever you cast a blue spell, each opponent mills a card.

Synchronous Battle Armor and equipped creature get +1/+1 for each artifact you control.
Whenever equipped creature attacks, tap up to three target creatures.
Reconfigure {3}{U}{U} ({3}{U}{U}: Attach to target creature you control; or unattach from a creature. Reconfigure only as a sorcery. While attached, this isn't a creature.)

Flying
Synchronous Hellkite enters with a +1/+1 counter for each other artifact you control.
Sacrifice three artifacts: Return Synchronous Hellkite from your graveyard to the battlefield.

Counter target spell unless its controller pays {X}. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

When Syncretic Master enters, look at the top X cards of your library, where X is the number of basic land types among lands you control. Put one them into your hand and the rest into your graveyard.

Menace, prowess

Wu Xing (Add effects based on the number of colors of mana spent to cast this spell.)
1 | Put a +1/+1 counter on each creature you control.
3 | Those creatures gain vigilance and deathtouch until end of turn.

Syndicate Sycophant can't block.
When a creature you control scavenges Syndicate Sycophant, you may search your library for a card named Syndicate Sycophant, reveal it, put it into your hand, then shuffle.
Scavenge {2}{B} ({2}{B}, Exile this card from your graveyard: Put a number of +1/+1 counters equal to this card's power on target creature. Scavenge only as a sorcery.)

Enchant creature
When Synergistic Curiosity enters, create a 2/2 blue Rogue creature token.
Enchanted creature gets +1/+1 and can't be blocked by creatures with flying.

{T}, Sacrifice Synthetic Seedling: Choose a basic land type. Create a tapped colorless enchantment land token with the chosen type.

Whenever a creature you control becomes blocked, you may return it to its owner's hand.
The first spell you cast during your postcombat main phase each turn costs {W}{U} less to cast. This effect reduces only the amount of colored mana you pay. (For example, if you cast a spell with mana cost {1}{U}, it costs {1} to cast.)

Flying
When Syrina's Brood enters, look at the top six cards of your library, then put them back in any order.

Flying
When Syrina, the Dragon Queen enters, gain control of target nonland permanent for as long as you control Syrina, the Dragon Queen.
{2}{U}: Exile Syrina, the Dragon Queen. Return her to the battlefield at the beginning of the next end step.

Enchant creature
Enchanted creature has deathtouch and “{1}{B}: Regenerate this creature.”

Look at target player's hand. Draw two cards, then discard a card.

Enchant creature
When Sythian Scripture enters, put two +1/+1 counters on enchanted creature.
Enchanted creature gets +1/+1 and has indestructible and lifelink if you controlled a white legendary creature or planeswalker as you cast Sythian Scripture.

Lifelink
Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)

Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Syurrai Traitor gets +1/+1 as long as you control a Plains.
{3}{W}: Create a 1/1 white Soldier creature token.

When Syzygy Navigator enters, exile target nonland card from an opponent's graveyard. Copy it. You may cast the copy. (You still pay its costs, including color. Copies of permanents enter as tokens.)
Whenever you cast a spell from anywhere other than your hand, draw a card, then discard a card.

During each of your turns, you may cast a copy of a card in an opponent's graveyard by exiling that card in addition to its other costs. (Copies of permanents enter as tokens.)

Flying
When T'nege, Skyguard enters, exile another target creature you control until T'nege leaves the battlefield. If you do, exile target creature an opponent controls until T'nege leaves the battlefield.