Retrieve the Esper

Create a 3/3 blue Robot Warrior artifact creature token. Then if this spell was cast from a graveyard, put two +1/+1 counters on that token.
Flashback {5}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Overkill

Target creature gets -0/-9999 until end of turn.

Sephiroth, Planet's Heir

Vigilance (Attacking doesn't cause this creature to tap.)
When Sephiroth enters, creatures your opponents control get -2/-2 until end of turn.
Whenever a creature an opponent controls dies, put a +1/+1 counter on Sephiroth.

Shambling Cie'th

This creature enters tapped.
Whenever you cast a noncreature spell, you may pay {B}. If you do, return this card from your graveyard to your hand.

Dreams of Laguna

Surveil 1, then draw a card. (To surveil 1, look at the top card of your library. You may put it into your graveyard.)
Flashback {3}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Shinra Reinforcements

When this creature enters, mill three cards and you gain 3 life. (To mill three cards, put the top three cards of your library into your graveyard.)

Treno, Dark City

This land enters tapped.
{T}: Add {U} or {B}.

Xande, Dark Mage

Menace (This creature can't be blocked except by two or more creatures.)
Xande gets +1/+1 for each noncreature, nonland card in your graveyard.

Sahagin

Whenever you cast a noncreature spell, if at least four mana was spent to cast it, put a +1/+1 counter on this creature and it can't be blocked this turn.

Ultimecia, Temporal Threat

When Ultimecia enters, tap all creatures your opponents control.
Whenever a creature you control deals combat damage to a player, draw a card.

Seymour Flux

At the beginning of your upkeep, you may pay 1 life. If you do, draw a card and put a +1/+1 counter on Seymour Flux.

Sephiroth's Intervention

Destroy target creature. You gain 2 life.

Magitek Scythe

A Test of Your Reflexes! — When this Equipment enters, you may attach it to target creature you control. If you do, that creature gains first strike until end of turn and must be blocked this turn if able.
Equipped creature gets +2/+1.
Equip {2}

Il Mheg Pixie

Flying
Whenever this creature attacks, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Evil Reawakened

Return target creature card from your graveyard to the battlefield with two additional +1/+1 counters on it.

Deadly Embrace

Destroy target creature an opponent controls. Then draw a card for each creature that died this turn.

Relm's Sketching

Create a token that's a copy of target artifact, creature, or land.

Undercity Dire Rat

Rat Tail — When this creature dies, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Al Bhed Salvagers

Whenever this creature or another creature or artifact you control dies, target opponent loses 1 life and you gain 1 life.