Midnight Oil

This enchantment enters with seven hour counters on it.
At the beginning of your draw step, draw an additional card and remove two hour counters from this enchantment.
Your maximum hand size is equal to the number of hour counters on this enchantment.
Whenever you discard a card, you lose 1 life.

Inspired Idea

Cleave {3}{U}{U} (You may cast this spell for its cleave cost. If you do, remove the words in square brackets.)
Draw three cards. [Your maximum hand size is reduced by three for the rest of the game.]

Body of Knowledge

Body of Knowledge's power and toughness are each equal to the number of cards in your hand.
You have no maximum hand size.
Whenever this creature is dealt damage, draw that many cards.

Othelm, Sigardian Outcast

{2}, {T}: Choose target creature card in your graveyard that was put there from the battlefield this turn. Return it to the battlefield tapped.
Partner—Friends forever (You can have two commanders if both have this ability.)

Wizard Class

(Gain the next level as a sorcery to add its ability.)
You have no maximum hand size.
{2}{U}: Level 2
When this Class becomes level 2, draw two cards.
{4}{U}: Level 3
Whenever you draw a card, put a +1/+1 counter on target creature you control.

Spellbook

Broken Bond

Destroy target artifact or enchantment. You may put a land card from your hand onto the battlefield.

Bond of Insight

Each player mills four cards. Return up to two instant and/or sorcery cards from your graveyard to your hand. Exile Bond of Insight.

Baleful Stare

Target opponent reveals their hand. You draw a card for each Mountain and red card in it.

Aeon Chronicler

Aeon Chronicler's power and toughness are each equal to the number of cards in your hand.
Suspend X—{X}{3}{U}. X can't be 0.
Whenever a time counter is removed from this card while it's exiled, draw a card.

Broken Fall

Return this enchantment to its owner's hand: Regenerate target creature.

Gnat Miser

Each opponent's maximum hand size is reduced by one.

Null Profusion

Skip your draw step.
Whenever you play a card, draw a card.
Your maximum hand size is two.

Balance of Power

If target opponent has more cards in hand than you, draw cards equal to the difference.

Cecily, Haunted Mage

Your maximum hand size is eleven.
Whenever Cecily, Haunted Mage attacks, you draw a card and you lose 1 life. Then if you have eleven or more cards in your hand, you may cast an instant or sorcery spell from your hand without paying its mana cost.
Partner—Friends forever (You can have two commanders if both have this ability.)

Triskaidekaphile

You have no maximum hand size.
At the beginning of your upkeep, if you have exactly thirteen cards in your hand, you win the game.
{3}{U}: Draw a card.

Akki Underling

As long as you have seven or more cards in hand, this creature gets +2/+1 and has first strike.

Ancient Excavation

Draw cards equal to the number of cards in your hand, then discard a card for each card drawn this way.
Basic landcycling {2} ({2}, Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.)