Spellseeker

When Spellseeker enters, you may search your library for an instant or sorcery card with mana value 2 or less, reveal it, put it into your hand, then shuffle.

Magosi, the Waterveil

Magosi, the Waterveil enters tapped.
{T}: Add {U}.
{U}, {T}: Put an eon counter on Magosi, the Waterveil. Skip your next turn.
{T}, Remove an eon counter from Magosi, the Waterveil and return it to its owner's hand: Take an extra turn after this one.

Gush

You may return two Islands you control to their owner's hand rather than pay this spell's mana cost.
Draw two cards.

Out of the Tombs

At the beginning of your upkeep, put two eon counters on Out of the Tombs, then mill cards equal to the number of eon counters on it.
If you would draw a card while your library has no cards in it, instead return a creature card from your graveyard to the battlefield. If you can't, you lose the game.

Scion of Halaster

Commander creatures you own have "The first time you would draw a card each turn, instead look at the top two cards of your library. Put one of them into your graveyard and the other back on top of your library. Then draw a card."

Saw in Half

Destroy target creature. If that creature dies this way, its controller creates two tokens that are copies of that creature, except their power is half that creature's power and their toughness is half that creature's toughness. Round up each time.

Consider

Surveil 1. (Look at the top card of your library. You may put it into your graveyard.)
Draw a card.

Dark Ritual

Shallow Grave

Return the top creature card of your graveyard to the battlefield. That creature gains haste until end of turn. Exile it at the beginning of the next end step.

Feed the Swarm

Destroy target creature or enchantment an opponent controls. You lose life equal to that permanent's mana value.

Gale, Waterdeep Prodigy

Whenever you cast an instant or sorcery spell from your hand, you may cast up to one target card of the other type from your graveyard. If a spell cast from your graveyard this way would be put into your graveyard, exile it instead.
Choose a Background (You can have a Background as a second commander.)

Thought Scour

Target player mills two cards.
Draw a card.

Solve the Equation

Search your library for an instant or sorcery card, reveal it, put it into your hand, then shuffle.

Fact or Fiction

Reveal the top five cards of your library. An opponent separates those cards into two piles. Put one pile into your hand and the other into your graveyard.

Frantic Search

Draw two cards, then discard two cards. Untap up to three lands.

Cabal Ritual

Add {B}{B}{B}.
Threshold — Add {B}{B}{B}{B}{B} instead if seven or more cards are in your graveyard.

Nesting Grounds

{T}: Add {C}.
{1}, {T}: Move a counter from target permanent you control onto another target permanent. Activate only as a sorcery.

Windfall

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

An Offer You Can't Refuse

Counter target noncreature spell. Its controller creates two Treasure tokens. (They're artifacts with "{T}, Sacrifice this token: Add one mana of any color.")

Scry 1. (Look at the top card of your library. You may put that card on the bottom.)
Draw a card.

Entomb

Search your library for a card, put that card into your graveyard, then shuffle.

Brain Freeze

Target player mills three cards.
Storm (When you cast this spell, copy it for each spell cast before it this turn. You may choose new targets for the copies.)