Jodah, the Unifier

Legendary creatures you control get +X/+X, where X is the number of legendary creatures you control.
Whenever you cast a legendary spell from your hand, exile cards from the top of your library until you exile a legendary nonland card with lesser mana value. You may cast that card without paying its mana cost. Put the rest on the bottom of your library in a random order.

Maelstrom Archangel

Flying
Whenever Maelstrom Archangel deals combat damage to a player, you may cast a spell from your hand without paying its mana cost.

The First Sliver

Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)
Sliver spells you cast have cascade.

Dragonspeaker Shaman

Dragon spells you cast cost {2} less to cast.

Horde of Notions

Vigilance, trample, haste
{W}{U}{B}{R}{G}: You may play target Elemental card from your graveyard without paying its mana cost.

Knight of the Stampede

Dinosaur spells you cast cost {2} less to cast.

Bosk Banneret

Treefolk spells and Shaman spells you cast cost {1} less to cast.

Herald of Slaanesh

Locus of Slaanesh — Demon spells you cast cost {2} less to cast.
Other Demons you control have haste.

Garth One-Eye

{T}: Choose a card name that hasn't been chosen from among Disenchant, Braingeyser, Terror, Shivan Dragon, Regrowth, and Black Lotus. Create a copy of the card with the chosen name. You may cast the copy. (You still pay its costs.)

Child of Alara

Trample
When Child of Alara dies, destroy all nonland permanents. They can't be regenerated.

Frogtosser Banneret

Haste
Goblin spells and Rogue spells you cast cost {1} less to cast.

Fusion Elemental

Sliver Legion

All Sliver creatures get +1/+1 for each other Sliver on the battlefield.

Otepec Huntmaster

Dinosaur spells you cast cost {1} less to cast.
{T}: Target Dinosaur gains haste until end of turn.

Niv-Mizzet Reborn

Flying
When Niv-Mizzet Reborn 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.

Stonybrook Banneret

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Merfolk spells and Wizard spells you cast cost {1} less to cast.

Brighthearth Banneret

Elemental spells and Warrior spells you cast cost {1} less to cast.
Reinforce 1—{1}{R} ({1}{R}, Discard this card: Put a +1/+1 counter on target creature.)

Morophon, the Boundless

Changeling (This card is every creature type.)
As Morophon, the Boundless enters, choose a creature type.
Spells of the chosen type you cast cost {W}{U}{B}{R}{G} less to cast. This effect reduces only the amount of colored mana you pay.
Other creatures you control of the chosen type get +1/+1.

Krosan Warchief

Beast spells you cast cost {1} less to cast.
{1}{G}: Regenerate target Beast.

Starnheim Aspirant

Angel spells you cast cost {2} less to cast.

Dragonlord's Servant

Dragon spells you cast cost {1} less to cast.

Stinkdrinker Daredevil

Giant spells you cast cost {2} less to cast.

Eye of Ugin

Colorless Eldrazi spells you cast cost {2} less to cast.
{7}, {T}: Search your library for a colorless creature card, reveal it, put it into your hand, then shuffle.

Niv-Mizzet, Guildpact

Flying, hexproof from multicolored
Whenever Niv-Mizzet, Guildpact deals combat damage to a player, it deals X damage to any target, target player draws X cards, and you gain X life, where X is the number of different color pairs among permanents you control that are exactly two colors.

Cromat

{W}{B}: Destroy target creature blocking or blocked by Cromat.
{U}{R}: Cromat gains flying until end of turn.
{B}{G}: Regenerate Cromat.
{R}{W}: Cromat gets +1/+1 until end of turn.
{G}{U}: Put Cromat on top of its owner's library.

Kinjalli's Caller

Dinosaur spells you cast cost {1} less to cast.

Goblin Warchief

Goblin spells you cast cost {1} less to cast.
Goblins you control have haste.

Ballyrush Banneret

Kithkin spells and Soldier spells you cast cost {1} less to cast.

Chromanticore

Bestow {2}{W}{U}{B}{R}{G} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
Flying, first strike, vigilance, trample, lifelink
Enchanted creature gets +4/+4 and has flying, first strike, vigilance, trample, and lifelink.

Sliver Gravemother

The "legend rule" doesn't apply to Slivers you control.
Each Sliver creature card in your graveyard has encore {X}, where X is its mana value.
Encore {5} ({5}, Exile this card from your graveyard: For each opponent, create a token copy that attacks that opponent this turn if able. They gain haste. Sacrifice them at the beginning of the next end step. Activate only as a sorcery.)

Sliver Hivelord

Sliver creatures you control have indestructible. (Damage and effects that say "destroy" don't destroy them.)