Jace, Cunning Castaway

+1: Whenever one or more creatures you control deal combat damage to a player this turn, draw a card, then discard a card.
−2: Create a 2/2 blue Illusion creature token with "When this token becomes the target of a spell, sacrifice it."
−5: Create two tokens that are copies of Jace, except they're not legendary.

Mystical Tutor

Search your library for an instant or sorcery card, reveal it, then shuffle and put that card on top.

Jace's Scrutiny

Target creature gets -4/-0 until end of turn.
Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")

Counterspell

Jace, Telepath Unbound

+1: Up to one target creature gets -2/-0 until your next turn.
−3: You may cast target instant or sorcery card from your graveyard this turn. If that spell would be put into your graveyard, exile it instead.
−9: You get an emblem with "Whenever you cast a spell, target opponent mills five cards."

Jace, Vryn's Prodigy

{T}: Draw a card, then discard a card. If there are five or more cards in your graveyard, exile Jace, then return him to the battlefield transformed under his owner's control.

Jace, Vryn's Prodigy // Jace, Telepath Unbound

Comparative Analysis

Surge {2}{U} (You may cast this spell for its surge cost if you or a teammate has cast another spell this turn.)
Target player draws two cards.

Jace's Archivist

{U}, {T}: Each player discards their hand, then draws cards equal to the greatest number of cards a player discarded this way.

Threads of Disloyalty

Enchant creature with mana value 2 or less
You control enchanted creature.

Blue Elemental Blast

Choose one —
• Counter target red spell.
• Destroy target red permanent.

Jace Beleren

+2: Each player draws a card.
−1: Target player draws a card.
−10: Target player mills twenty cards.

Strategic Planning

Look at the top three cards of your library. Put one of them into your hand and the rest into your graveyard.

Contingency Plan

Surveil 5. (Look at the top five cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)

Unity of Purpose

Support 2. (Put a +1/+1 counter on each of up to two target creatures.)
Untap each creature you control with a +1/+1 counter on it.

Jace's Mindseeker

Flying
When this creature enters, target opponent mills five cards. You may cast an instant or sorcery spell from among them without paying its mana cost.

Laboratory Maniac

If you would draw a card while your library has no cards in it, you win the game instead.

Negate

Imaginary Threats

Creatures target opponent controls attack this turn if able. During that player's next untap step, creatures they control don't untap.
Cycling {2} ({2}, Discard this card: Draw a card.)

Brainstorm

Draw three cards, then put two cards from your hand on top of your library in any order.