Galvanoth

At the beginning of your upkeep, you may look at the top card of your library. You may cast it without paying its mana cost if it's an instant or sorcery spell.

Nightveil Specter

Flying
Whenever Nightveil Specter deals combat damage to a player, that player exiles the top card of their library.
You may play lands and cast spells from among cards exiled with Nightveil Specter.

Jeleva, Nephalia's Scourge

Flying
When Jeleva, Nephalia's Scourge enters, each player exiles the top X cards of their library, where X is the amount of mana spent to cast Jeleva.
Whenever Jeleva attacks, you may cast an instant or sorcery spell from among cards exiled with Jeleva without paying its mana cost.

Mnemonic Betrayal

Exile all opponents' graveyards. You may cast spells from among those cards this turn, and mana of any type can be spent to cast them. At the beginning of the next end step, if any of those cards remain exiled, return them to their owners' graveyards.
Exile Mnemonic Betrayal.

Nightscape Familiar

Blue spells and red spells you cast cost {1} less to cast.
{1}{B}: Regenerate Nightscape Familiar.

Gonti, Lord of Luxury

Deathtouch
When Gonti, Lord of Luxury enters, look at the top four cards of target opponent's library, exile one of them face down, then put the rest on the bottom of that library in a random order. You may cast that card for as long as it remains exiled, and mana of any type can be spent to cast that spell.

Dark Ritual

Frantic Search

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

Goblin Electromancer

Instant and sorcery spells you cast cost {1} less to cast.

Terminate

Destroy target creature. It can't be regenerated.

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.

Thief of Sanity

Flying
Whenever Thief of Sanity deals combat damage to a player, look at the top three cards of that player's library, exile one of them face down, then put the rest into their graveyard. You may cast that card for as long as it remains exiled, and mana of any type can be spent to cast that spell.

Oblivion Sower

When you cast this spell, target opponent exiles the top four cards of their library, then you may put any number of land cards that player owns from exile onto the battlefield under your control.

Guttersnipe

Whenever you cast an instant or sorcery spell, this creature deals 2 damage to each opponent.