Reflexes

Enchant creature (Target a creature as you cast this. This card enters attached to that creature.)
Enchanted creature has first strike. (It deals combat damage before creatures without first strike.)

Retromancer

Whenever this creature becomes the target of a spell or ability, this creature deals 3 damage to that spell or ability's controller.

Monk Realist

When this creature enters, destroy target enchantment.

Rumbling Crescendo

At the beginning of your upkeep, you may put a verse counter on this enchantment.
{R}, Sacrifice this enchantment: Destroy up to X target lands, where X is the number of verse counters on this enchantment.

Scald

Whenever a player taps an Island for mana, this enchantment deals 1 damage to that player.

Scoria Wurm

At the beginning of your upkeep, flip a coin. If you lose the flip, return this creature to its owner's hand.

Scrap

Destroy target artifact.
Cycling {2} ({2}, Discard this card: Draw a card.)

Shivan Hellkite

Flying (This creature can't be blocked except by creatures with flying or reach.)
{1}{R}: This creature deals 1 damage to any target.

Shivan Raptor

First strike, haste
Echo {2}{R} (At the beginning of your upkeep, if this came under your control since the beginning of your last upkeep, sacrifice it unless you pay its echo cost.)

Shiv's Embrace

Enchant creature
Enchanted creature gets +2/+2 and has flying.
{R}: Enchanted creature gets +1/+0 until end of turn.

Shower of Sparks

Shower of Sparks deals 1 damage to target creature and 1 damage to target player or planeswalker.

Sneak Attack

{R}: You may put a creature card from your hand onto the battlefield. That creature gains haste. Sacrifice the creature at the beginning of the next end step.

Steam Blast

Steam Blast deals 2 damage to each creature and each player.

Opal Acrolith

Whenever an opponent casts a creature spell, if this permanent is an enchantment, it becomes a 2/4 Soldier creature.
{0}: This permanent becomes an enchantment.

Sulfuric Vapors

If a red spell would deal damage to a permanent or player, it deals that much damage plus 1 to that permanent or player instead.

Thundering Giant

Haste (This creature can attack and {T} as soon as it comes under your control.)

Urza's Saga