Wild Mongrel

Discard a card: Wild Mongrel gets +1/+1 and becomes the color of your choice until end of turn.

Basking Rootwalla

{1}{G}: Basking Rootwalla gets +2/+2 until end of turn. Activate only once each turn.
Madness {0} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Nimble Mongoose

Shroud (This creature can't be the target of spells or abilities.)
Threshold — Nimble Mongoose gets +2/+2 as long as seven or more cards are in your graveyard.

Obsessive Search

Draw a card.
Madness {U} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Just the Wind

Return target creature to its owner's hand.
Madness {U} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Careful Study

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.

Aquamoeba

Discard a card: Switch Aquamoeba's power and toughness until end of turn.

Circular Logic

Counter target spell unless its controller pays {1} for each card in your graveyard.
Madness {U} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Arrogant Wurm

Trample
Madness {2}{G} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)