Enfeeblement

Enchant creature (Target a creature as you cast this. This card enters the battlefield attached to that creature.)
Enchanted creature gets -2/-2.

Farfinder

Vigilance
When Farfinder enters the battlefield, you may search your library for a basic land card, reveal it, put it into your hand, then shuffle.

Quag Sickness

Enchant creature
Enchanted creature gets -1/-1 for each Swamp you control.

Eternal Thirst

Enchant creature
Enchanted creature has lifelink and "Whenever a creature an opponent controls dies, put a +1/+1 counter on this creature." (Damage dealt by a creature with lifelink also causes its controller to gain that much life.)

Dusk Legion Zealot

When Dusk Legion Zealot enters the battlefield, you draw a card and you lose 1 life.

Blessing of Leeches

Flash
Enchant creature
At the beginning of your upkeep, you lose 1 life.
{0}: Regenerate enchanted creature.

Nyx Infusion

Enchant creature
Enchanted creature gets +2/+2 as long as it's an enchantment. Otherwise, it gets -2/-2.

Phyresis

Enchant creature
Enchanted creature has infect. (It deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)

Parasitic Implant

Enchant creature
At the beginning of your upkeep, enchanted creature's controller sacrifices it and you create a 1/1 colorless Phyrexian Myr artifact creature token.

Liliana's Specter

Flying
When Liliana's Specter enters the battlefield, each opponent discards a card.

Stab Wound

Enchant creature
Enchanted creature gets -2/-2.
At the beginning of the upkeep of enchanted creature's controller, that player loses 2 life.

Necromancer's Magemark

Enchant creature
Creatures you control that are enchanted get +1/+1.
If a creature you control that's enchanted would die, return it to its owner's hand instead.

Thorn of the Black Rose

Deathtouch
When Thorn of the Black Rose enters the battlefield, you become the monarch.

Endless Scream

Enchant creature
Endless Scream enters the battlefield with X scream counters on it.
Enchanted creature gets +1/+0 for each scream counter on Endless Scream.

Rotting Rats

When Rotting Rats enters the battlefield, each player discards a card.
Unearth {1}{B} ({1}{B}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)

Skyscanner

Flying
When Skyscanner enters the battlefield, draw a card.

Mire's Grasp

Enchant creature
Enchanted creature gets -3/-3.

Parallax Dementia

Enchant creature
Fading 1 (This enchantment enters the battlefield with one fade counter on it. At the beginning of your upkeep, remove a fade counter from it. If you can't, sacrifice it.)
Enchanted creature gets +3/+2.
When Parallax Dementia leaves the battlefield, destroy enchanted creature. That creature can't be regenerated.

Boon of Emrakul

Enchant creature
Enchanted creature gets +3/-3.

Lingering Death

Enchant creature
At the beginning of the end step of enchanted creature's controller, that player sacrifices that creature.

Grim Guardian

Constellation — Whenever Grim Guardian or another enchantment enters the battlefield under your control, each opponent loses 1 life.

Miasmic Mummy

When Miasmic Mummy enters the battlefield, each player discards a card.

Dark Favor

Enchant creature
When Dark Favor enters the battlefield, you lose 1 life.
Enchanted creature gets +3/+1.

Yoke of the Damned

Enchant creature
When a creature dies, destroy enchanted creature.

Dead Weight

Enchant creature
Enchanted creature gets -2/-2.

Maggot Therapy

Flash
Enchant creature
Enchanted creature gets +2/-2.

Hateful Eidolon

Lifelink
Whenever an enchanted creature dies, draw a card for each Aura you controlled that was attached to it.

Gray Merchant of Asphodel

When Gray Merchant of Asphodel enters the battlefield, each opponent loses X life, where X is your devotion to black. You gain life equal to the life lost this way. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)

Infernal Scarring

Enchant creature
Enchanted creature gets +2/+0 and has "When this creature dies, draw a card."

Spinal Graft

Enchant creature
Enchanted creature gets +3/+3.
When enchanted creature becomes the target of a spell or ability, destroy that creature. It can't be regenerated.

Debilitating Injury

Kagemaro's Clutch

Enchant creature
Enchanted creature gets -X/-X, where X is the number of cards in your hand.

Grisly Transformation

Enchant creature
When Grisly Transformation enters the battlefield, draw a card.
Enchanted creature has intimidate. (It can't be blocked except by artifact creatures and/or creatures that share a color with it.)