Eaten by Piranhas

Flash (You may cast this spell any time you could cast an instant.)
Enchant creature
Enchanted creature loses all abilities and is a black Skeleton creature with base power and toughness 1/1. (It loses all other colors, card types, and creature types.)

Quick Study

Kiora, the Rising Tide

When Kiora enters, draw two cards, then discard two cards.
Threshold — Whenever Kiora attacks, if there are seven or more cards in your graveyard, you may create Scion of the Deep, a legendary 8/8 blue Octopus creature token.

Dimir Guildgate

This land enters tapped.
{T}: Add {U} or {B}.

Chart a Course

Draw two cards. Then discard a card unless you attacked this turn.

Refute

Counter target spell. Draw a card, then discard a card.

Uncharted Voyage

Target creature's owner puts it on their choice of the top or bottom of their library.
Surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Rune-Sealed Wall

Defender
{T}: Surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Cephalid Inkmage

When this creature enters, surveil 3. (Look at the top three cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)
Threshold — This creature can't be blocked as long as there are seven or more cards in your graveyard.

Billowing Shriekmass

Flying
When this creature enters, mill three cards. (Put the top three cards of your library into your graveyard.)
Threshold — This creature gets +2/+1 as long as there are seven or more cards in your graveyard.

Dreadwing Scavenger

Flying
Whenever this creature enters or attacks, draw a card, then discard a card.
Threshold — This creature gets +1/+1 and has deathtouch as long as there are seven or more cards in your graveyard.

Strix Lookout

Flying, vigilance (Attacking doesn't cause this creature to tap.)
{1}{U}, {T}: Draw a card, then discard a card.