Paragon of Open Graves

Other black creatures you control get +1/+1.
{2}{B}, {T}: Another target black creature you control gains deathtouch until end of turn. (Any amount of damage it deals to a creature is enough to destroy it.)

Mortus Strider

When Mortus Strider dies, return it to its owner's hand.

Cinderbones

Wither (This deals damage to creatures in the form of -1/-1 counters.)
{1}{B}: Regenerate Cinderbones.

Restless Dead

Uchbenbak, the Great Mistake

Vigilance, menace
Descend 8 — {4}{U}{B}: Return Uchbenbak, the Great Mistake from your graveyard to the battlefield with a finality counter on it. Activate only if there are eight or more permanent cards in your graveyard and only as a sorcery. (If a creature with a finality counter on it would die, exile it instead.)

Death Baron

Skeletons you control and other Zombies you control get +1/+1 and have deathtouch. (Any amount of damage they deal to a creature is enough to destroy it.)

Skeleton Crew

Each other creature you control that's a Skeleton or Pirate gets +1/+1.
Whenever one or more creature cards leave your graveyard, create a 2/2 black Skeleton Pirate creature token. (This ability triggers only from the battlefield.)
{5}{B}: Return Skeleton Crew from your graveyard to the battlefield tapped.

Gutterbones

Gutterbones enters tapped.
{1}{B}: Return Gutterbones from your graveyard to your hand. Activate only during your turn and only if an opponent lost life this turn.

Skeleton Ship

When you control no Islands, sacrifice Skeleton Ship.
{T}: Put a -1/-1 counter on target creature.

Drudge Skeletons

{B}: Regenerate Drudge Skeletons. (The next time this creature would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Underworld Sentinel

Whenever Underworld Sentinel attacks, exile target creature card from your graveyard.
When Underworld Sentinel dies, put all cards exiled with it onto the battlefield.

Reassembling Skeleton

{1}{B}: Return this card from your graveyard to the battlefield tapped.

Persistent Specimen

{2}{B}: Return Persistent Specimen from your graveyard to the battlefield tapped.

Corpses of the Lost

Skeletons you control get +1/+0 and have haste.
When Corpses of the Lost enters, create a 2/2 black Skeleton Pirate creature token.
At the beginning of your end step, if you descended this turn, you may pay 1 life. If you do, return Corpses of the Lost to its owner's hand. (You descended if a permanent card was put into your graveyard from anywhere.)

Tenacious Dead

When Tenacious Dead dies, you may pay {1}{B}. If you do, return it to the battlefield tapped under its owner's control.

Eaten by Piranhas

Flash (You may cast this spell any time you could cast an instant.)
Enchant creature
Enchanted creature loses all abilities and is a black Skeleton creature with base power and toughness 1/1. (It loses all other colors, card types, and creature types.)