Reclusive Taxidermist

This creature gets +3/+2 as long as there are four or more creature cards in your graveyard.
{T}: Add one mana of any color.

Niv-Mizzet Reborn

Flying
When Niv-Mizzet enters, reveal the top ten cards of your library. For each color pair, choose a card that's exactly those colors from among them. Put the chosen cards into your hand and the rest on the bottom of your library in a random order.

Leyline Prowler

Deathtouch, lifelink
{T}: Add one mana of any color.

Bronze Walrus

When this creature enters, scry 2. (Look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)
{T}: Add one mana of any color.

Gemhide Sliver

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

Ilysian Caryatid

{T}: Add one mana of any color. If you control a creature with power 4 or greater, add two mana of any one color instead.

Beastcaller Savant

Haste
{T}: Add one mana of any color. Spend this mana only to cast a creature spell.

Harvester Druid

{T}: Add one mana of any color that a land you control could produce.

Ornithopter of Paradise

Channeler Initiate

When this creature enters, put three -1/-1 counters on target creature you control.
{T}, Remove a -1/-1 counter from this creature: Add one mana of any color.

Undercellar Myconid

Whenever this creature enters or dies, create a 1/1 green Saproling creature token.
{T}: Add one mana of any color.

Drover of the Mighty

This creature gets +2/+2 as long as you control a Dinosaur.
{T}: Add one mana of any color.

Humble Naturalist

{T}: Add one mana of any color. Spend this mana only to cast a creature spell.

Rootcoil Creeper

{T}: Add one mana of any color.
{T}: Add two mana of any one color. Spend this mana only to cast spells from your graveyard.
{G}{U}, {T}, Exile this creature: Return target card with flashback you own from exile to your hand.

Manaweft Sliver

Sliver creatures you control have "{T}: Add one mana of any color."

Armored Scrapgorger

This creature gets +3/+0 as long as it has three or more oil counters on it.
{T}: Add one mana of any color.
Whenever this creature becomes tapped, exile target card from a graveyard and put an oil counter on this creature.

Paradise Druid

This creature has hexproof as long as it's untapped. (It can't be the target of spells or abilities your opponents control.)
{T}: Add one mana of any color.

Llanowar Loamspeaker

{T}: Add one mana of any color.
{T}: Target land you control becomes a 3/3 Elemental creature with haste until end of turn. It's still a land. Activate only as a sorcery.