mtg.wtf

Fear
When Squealing Devil enters the battlefield, you may pay {X}. If you do, target creature gets +X/+0 until end of turn.
When Squealing Devil enters the battlefield, sacrifice it unless {B} was spent to cast it.

When Squidnapper enters the battlefield, gain control of target creature an opponent controls until Squidnapper leaves the battlefield or that player pays the ransom.
Ransom — {6} and 2 life

Enchant creature
Enchanted creature gets +1/+1 and has lifelink.
When Squire's Devotion enters the battlefield, create a 1/1 white Vampire creature token with lifelink.

When Squirrel Dealer enters the battlefield, ask a person outside the game "Do you like Squirrels?" If they do, create a 1/1 green Squirrel creature token.

When Squirrel Sanctuary enters the battlefield, create a 1/1 green Squirrel creature token.
Whenever a nontoken creature you control dies, you may pay {1}. If you do, return Squirrel Sanctuary to its owner's hand.

When Squirrel Squatters enters the battlefield, open an Attraction.
Whenever Squirrel Squatters attacks, create a 1/1 green Squirrel creature token that's tapped and attacking for each Attraction you've visited this turn.

When Stack of Paperwork enters the battlefield, draw a card.
Combat damage uses the stack. (Combat damage assignment can be responded to before damage is dealt.)

When Stadium Vendors enters the battlefield, choose a player. That player adds two mana of any one color they choose.

When Staff of the Storyteller enters the battlefield, create a 1/1 white Spirit creature token with flying.
Whenever you create one or more creature tokens, put a story counter on Staff of the Storyteller.
{W}, {T}, Remove a story counter from Staff of the Storyteller: Draw a card.

When Stagecoach Security enters the battlefield, creatures you control get +1/+1 and gain vigilance until end of turn.
Plot {3}{W}

When Stalking Leonin enters the battlefield, secretly choose an opponent.
Reveal the player you chose: Exile target creature that's attacking you if it's controlled by the chosen player. Activate only once.

When Stalking Yeti enters the battlefield, if it's on the battlefield, it deals damage equal to its power to target creature an opponent controls and that creature deals damage equal to its power to Stalking Yeti.
{2}{S}: Return Stalking Yeti to its owner's hand. Activate only as a sorcery.

When Stalwarts of Osgiliath enters the battlefield, the Ring tempts you.
Whenever you draw your second card each turn, put a +1/+1 counter on Stalwarts of Osgiliath.

When Stangg enters the battlefield, create Stangg Twin, a legendary 3/4 red and green Human Warrior creature token. Exile that token when Stangg leaves the battlefield. Sacrifice Stangg when that token leaves the battlefield.

Flash
Enchant creature you control
When Starlit Mantle enters the battlefield, enchanted creature gains hexproof until end of turn.
Enchanted creature gets +1/+1.

When Starving Revenant enters the battlefield, surveil 2. Then for each card you put on top of your library, you draw a card and you lose 3 life.
Descend 8 — Whenever you draw a card, if there are eight or more permanent cards in your graveyard, target opponent loses 1 life and you gain 1 life.

Flash
When Stasis Snare enters the battlefield, exile target creature an opponent controls until Stasis Snare leaves the battlefield.

When Static Net enters the battlefield, exile target nonland permanent an opponent controls until Static Net leaves the battlefield.
When Static Net enters the battlefield, you gain 2 life and create a tapped Powerstone token.

When Staunch Crewmate enters the battlefield, look at the top four cards of your library. You may reveal an artifact or Pirate card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

When Staunch Defenders enters the battlefield, you gain 4 life.

Vigilance
When Staunch Throneguard enters the battlefield, you become the monarch.

Deathtouch
When Steady-Handed Mook enters the battlefield, it assembles a Contraption. (Put the top card of your Contraption deck face up onto one of your sprockets.)

Flying, vigilance
When Steamcore Scholar enters the battlefield, draw two cards. Then discard two cards unless you discard an instant or sorcery card or a creature card with flying.

When Steamcore Weird enters the battlefield, if {R} was spent to cast it, it deals 2 damage to any target.

When Steamflogger of the Month enters the battlefield, it assembles a Contraption for each Contraption you control. (To assemble a Contraption, put the top card of your Contraption deck face up onto one of your sprockets.)