Spinneret Sliver

Power Sink

Counter target spell unless its controller pays {X}. If that player doesn't, they tap all lands with mana abilities they control and lose all unspent mana.

Muscle Sliver

Counterspell

Rancor

Enchant creature
Enchanted creature gets +2/+0 and has trample.
When Rancor is put into a graveyard from the battlefield, return Rancor to its owner's hand.

Virulent Sliver

All Sliver creatures have poisonous 1. (Whenever a Sliver deals combat damage to a player, that player gets a poison counter. A player with ten or more poison counters loses the game.)

Predatory Sliver

Giant Growth

Target creature gets +3/+3 until end of turn.

Gemhide Sliver

All Slivers have "{T}: Add one mana of any color."

Winged Sliver

Brainstorm

Draw three cards, then put two cards from your hand on top of your library in any order.