The Ur-Dragon

Eminence — As long as The Ur-Dragon is in the command zone or on the battlefield, other Dragon spells you cast cost {1} less to cast.
Flying
Whenever one or more Dragons you control attack, draw that many cards, then you may put a permanent card from your hand onto the battlefield.

Fierce Empath

When this creature enters, you may search your library for a creature card with mana value 6 or greater, reveal it, put it into your hand, then shuffle.

Arcane Adaptation

As this enchantment enters, choose a creature type.
Creatures you control are the chosen type in addition to their other types. The same is true for creature spells you control and creature cards you own that aren't on the battlefield.

Role Reversal

Exchange control of two target permanents that share a permanent type.

Fractured Identity

Exile target nonland permanent. Each player other than its controller creates a token that's a copy of it.

Blim, Comedic Genius

Flying
Whenever Blim deals combat damage to a player, that player gains control of target permanent you control. Then each player loses life and discards cards equal to the number of permanents they control but don't own.

Trade the Helm

Exchange control of target artifact or creature you control and target artifact or creature an opponent controls.
Cycling {2} ({2}, Discard this card: Draw a card.)

Sudden Substitution

Split second (As long as this spell is on the stack, players can't cast spells or activate abilities that aren't mana abilities.)
Exchange control of target noncreature spell and target creature. Then the spell's controller may choose new targets for it.

Daring Thief

Inspired — Whenever this creature becomes untapped, you may exchange control of target nonland permanent you control and target permanent an opponent controls that shares a card type with it.

Maskwood Nexus

Creatures you control are every creature type. The same is true for creature spells you control and creature cards you own that aren't on the battlefield.
{3}, {T}: Create a 2/2 blue Shapeshifter creature token with changeling. (It is every creature type.)

Shrewd Negotiation

Exchange control of target artifact you control and target artifact or creature you don't control.

Karrthus, Tyrant of Jund

Flying, haste
When Karrthus enters, gain control of all Dragons, then untap all Dragons.
Other Dragon creatures you control have haste.

Gauntlets of Chaos

{5}, Sacrifice this artifact: Exchange control of target artifact, creature, or land you control and target permanent an opponent controls that shares one of those types with it. If those permanents are exchanged this way, destroy all Auras attached to them.

Legerdemain

Exchange control of target artifact or creature and another target permanent that shares one of those types with it. (This effect lasts indefinitely.)

Harmless Offering

Target opponent gains control of target permanent you control.

Conspiracy

As this enchantment enters, choose a creature type.
Creatures you control are the chosen type. The same is true for creature spells you control and creature cards you own that aren't on the battlefield.