Silverquill Lecturer

Creature spells you cast have demonstrate. (Whenever you cast a creature spell, you may copy it. If you do, choose an opponent to also copy it. Each copy becomes a token.)

The Twelfth Doctor

The first spell you cast from anywhere other than your hand each turn has demonstrate. (When you cast that spell, you may copy it. If you do, choose an opponent to also copy it. A copy of a permanent spell becomes a token.)
Whenever you copy a spell, put a +1/+1 counter on The Twelfth Doctor.

Creative Technique

Demonstrate (When you cast this spell, you may copy it. If you do, choose an opponent to also copy it.)
Shuffle your library, then reveal cards from the top of it until you reveal a nonland card. Exile that card and put the rest on the bottom of your library in a random order. You may cast the exiled card without paying its mana cost.

Play of the Game

Assist (Another player can pay up to {6} of this spell's cost.)
Exile all nonland permanents.

Romana II

Vigilance
{1}, {T}: Create a tapped token that's a copy of target token that entered this turn.
Doctor's companion (You can have two commanders if the other is the Doctor.)

Spellweaver Duo

Assist (Another player can pay up to {6} of this spell's cost.)
When Spellweaver Duo enters, you may return target tapped creature to its owner's hand.

Replication Technique

Demonstrate (When you cast this spell, you may copy it. If you do, choose an opponent to also copy it. Players may choose new targets for their copies.)
Create a token that's a copy of target permanent you control.

Skystreamer

Assist (Another player can pay up to {4} of this spell's cost.)
Flying
When Skystreamer enters, target player gains 4 life.

Excavation Technique

Demonstrate (When you cast this spell, you may copy it. If you do, choose an opponent to also copy it. Players may choose new targets for their copies.)
Destroy target nonland permanent. Its controller creates two Treasure tokens.

Magma Hellion

Assist (Another player can pay up to {6} of this spell's cost.)
Trample, haste

Huddle Up

Assist (Another player can pay up to {2} of this spell's cost.)
Two target players each draw a card.

Out of Bounds

Assist (Another player can pay up to {3} of this spell's cost.)
Counter target spell.

Lava-Field Overlord

Assist (Another player can pay up to {7} of this spell's cost.)
Flying
When Lava-Field Overlord enters, it deals 4 damage to target creature an opponent controls.

Game Plan

Assist (Another player can pay up to {5} of this spell's cost.)
Each player shuffles their hand and graveyard into their library, then draws seven cards. Exile Game Plan.

Dwarven Lightsmith

Assist (Another player can pay up to {5} of this spell's cost.)
When Dwarven Lightsmith enters, creatures your team controls get +1/+1 until end of turn.

Bring Down

Assist (Another player can pay up to {3} of this spell's cost.)
Destroy target creature with power 4 or greater.