Vigilance

Whenever Sentinel of the Nameless City enters or attacks, create a Map token. (It's an artifact with ", , Sacrifice this artifact: Target creature you control explores. Activate only as a sorcery.")

Haste

As long as an artifact entered the battlefield under your control this turn, creatures you control get +2/+2.

Battalion — Whenever Sentinel Sarah Lyons and at least two other creatures attack, Sentinel Sarah Lyons deals damage equal to the number of artifacts you control to target player.

Vigilance, reach

Whenever an instant or sorcery spell is cast during your turn, Sentinel Tower deals damage to any target equal to 1 plus the number of instant and sorcery spells cast before that spell this turn.

Flash

Enchant creature

Enchanted creature gets +1/+2 and has vigilance.

Addendum — When Sentinel's Mark enters, if you cast it during your main phase, enchanted creature gains lifelink until end of turn.

Flash

This spell costs less to cast for each creature attacking you.

When Sentry Bot enters, you get for each creature attacking you.

At the beginning of combat on your turn, you may pay . If you do, put a +1/+1 counter on each creature you control.

Flying, vigilance

, Pay 3 life: Regenerate Sentry of the Underworld.

When Separatist Voidmage enters, you may return target creature to its owner's hand.

Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)

Whenever Septic Rats attacks, if defending player is poisoned, it gets +1/+1 until end of turn.

Intimidate (This creature can't be blocked except by artifact creatures and/or creatures that share a color with it.)

When Sepulchral Primordial enters, for each opponent, you may put up to one target creature card from that player's graveyard onto the battlefield under your control.

: Add .

, , Sacrifice Sequestered Stash: Mill five cards. Then you may put an artifact card from your graveyard on top of your library.

Flying, lifelink

Flying

Whenever Seraph of New Phyrexia attacks, you may sacrifice another creature or artifact. If you do, Seraph of New Phyrexia gets +2/+1 until end of turn.

Flying

: Seraph of the Scales gains vigilance until end of turn.

: Seraph of the Scales gains deathtouch until end of turn.

Afterlife 2 (When this creature dies, create two 1/1 white and black Spirit creature tokens with flying.)

Flying

Prevent all combat damage that would be dealt to Seraph of the Sword.

Equipped creature gets +2/+2.

Whenever equipped creature attacks the player with the most life or tied for most life, create a 4/4 white Angel creature token with flying that's tapped and attacking that player.

Equip

Flying

At the beginning of your upkeep, sacrifice a land. If you sacrifice an Island this way, Serendib Djinn deals 3 damage to you.

When you control no lands, sacrifice Serendib Djinn.

: Target creature other than Serendib Sorcerer has base power and toughness 0/2 until end of turn.

Whenever Serene Master blocks, exchange its power and the power of target creature it's blocking until end of combat.

Shuffle Serene Remembrance and up to three target cards from a single graveyard into their owners' libraries.

Whenever you gain life, you may pay . If you do, put a +1/+1 counter on target creature.

At the beginning of your upkeep, destroy all artifacts and enchantments. They can't be regenerated.

Kicker (You may pay an additional as you cast this spell.)

When Sergeant-at-Arms enters, if it was kicked, create two 1/1 white Soldier creature tokens.

, : Create a 1/1 colorless Snake artifact creature token. It has "Whenever this creature deals damage to a player, that player gets a poison counter." (A player with ten or more poison counters loses the game.)

Krakens, Leviathans, Octopuses, and Serpents you control can't be blocked except by Krakens, Leviathans, Octopuses, and Serpents.

When Serpent Warrior enters, you lose 3 life.

Landfall — Whenever a land you control enters,

Augment (, Reveal this card from your hand: Combine it with target host. Augment only as a sorcery.)

Whenever Serpentine Basilisk deals combat damage to a creature, destroy that creature at end of combat.

Morph (You may cast this card face down as a 2/2 creature for . Turn it face up any time for its morph cost.)

: Serpentine Kavu gains haste until end of turn.

Target creature gains deathtouch until end of turn. (Any amount of damage it deals to a creature is enough to destroy it.)

Flying

: Target attacking or blocking creature gets +2/+2 until end of turn.

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

As long as you have 30 or more life, Serra Ascendant gets +5/+5 and has flying.

You can't cast Serra Avenger during your first, second, or third turns of the game.

Flying, vigilance

Enchant creature

At the beginning of your upkeep, sacrifice Serra Bestiary unless you pay .

Enchanted creature can't attack or block, and its activated abilities with in their costs can't be activated.

Flying, vigilance

: Prevent the next 1 damage that would be dealt to any target this turn.

, : Target creature gains vigilance until end of turn.

Flying

Whenever another creature you control with power 2 or less enters, put two +1/+1 counters on that creature.

+2: Creatures you control with flying get +1/+1 until end of turn.

−3: Create a 4/4 white Angel creature token with flying and vigilance.

−6: You get an emblem with "If you control a creature, damage that would reduce your life total to less than 1 reduces it to 1 instead."

Creatures you control have vigilance. (Attacking doesn't cause them to tap.)

Enchant creature

Enchanted creature gets +2/+2 and has flying and vigilance. (Attacking doesn't cause it to tap.)

Flying (This creature can't be blocked except by creatures with flying or reach.)

Vigilance (Attacking doesn't cause this creature to tap.)

Other creatures you control have vigilance.

At the beginning of your upkeep, you may put a verse counter on Serra's Liturgy.

, Sacrifice Serra's Liturgy: Destroy up to X target artifacts and/or enchantments, where X is the number of verse counters on Serra's Liturgy.

Serrated Arrows enters with three arrowhead counters on it.

At the beginning of your upkeep, if there are no arrowhead counters on Serrated Arrows, sacrifice it.

, Remove an arrowhead counter from Serrated Arrows: Put a -1/-1 counter on target creature.

When Serrated Scorpion dies, it deals 2 damage to each opponent and you gain 2 life.

Flying

When Serum Raker dies, each player discards a card.

Flying

Whenever you cast a noncreature spell, put an oil counter on Serum Sovereign.

, Remove an oil counter from Serum Sovereign: Draw a card, then scry 2.

When Serum Visionary enters, draw a card, then scry 2.

Flying

Whenever you cast a noncreature spell, put an oil counter on Serum-Core Chimera.

Remove three oil counters from Serum-Core Chimera: Draw a card. Then you may discard a nonland card. When you discard a card this way, Serum-Core Chimera deals 3 damage to target creature or planeswalker. Activate only as a sorcery.

When Servant of the Conduit enters, you get (two energy counters).

, Pay : Add one mana of any color.

Deathtouch

Whenever Servant of the Stinger deals combat damage to a player, if you've committed a crime this turn, you may sacrifice Servant of the Stinger. If you do, search your library for a card, put it into your hand, then shuffle. (Targeting opponents, anything they control, and/or cards in their graveyards is a crime.)