Lonely Sandbar

Lonely Sandbar enters tapped.
{T}: Add {U}.
Cycling {U} ({U}, Discard this card: Draw a card.)

Homarid

Homarid enters with a tide counter on it.
At the beginning of your upkeep, put a tide counter on Homarid.
As long as there is exactly one tide counter on Homarid, it gets -1/-1.
As long as there are exactly three tide counters on Homarid, it gets +1/+1.
Whenever there are four or more tide counters on Homarid, remove all tide counters from it.

Ruin Crab

Landfall — Whenever a land you control enters, each opponent mills three cards. (To mill a card, a player puts the top card of their library into their graveyard.)

Island

Purple-Crystal Crab

When Purple-Crystal Crab dies, draw a card.

Howling Mine

At the beginning of each player's draw step, if Howling Mine is untapped, that player draws an additional card.

Hedron Crab

Landfall — Whenever a land you control enters, target player mills three cards.

Pongify

Destroy target creature. It can't be regenerated. Its controller creates a 3/3 green Ape creature token.

Khod, Etlan Shiis Envoy

All lands are Islands in addition to their other types.
Other Homarids, Camarids, Cephalids, Nautilids, and Merfolk you control get +1/+1.

Castle Vantress

Castle Vantress enters tapped unless you control an Island.
{T}: Add {U}.
{2}{U}{U}, {T}: Scry 2.

Brainstorm

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

Counterspell

Viscerid Deepwalker

{U}: Viscerid Deepwalker gets +1/+0 until end of turn.
Suspend 4—{U} (Rather than cast this card from your hand, you may pay {U} and exile it with four time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost. It has haste.)

Homarid Spawning Bed

{1}{U}{U}, Sacrifice a blue creature: Create X 1/1 blue Camarid creature tokens, where X is the sacrificed creature's mana value.

Homarid Explorer

When Homarid Explorer enters, target player mills four cards.

Teferi's Tutelage

When Teferi's Tutelage enters, draw a card, then discard a card.
Whenever you draw a card, target opponent mills two cards. (They put the top two cards of their library into their graveyard.)