msem-instigator

Flash
When Seabreen Nullmage enters, counter target activated or triggered ability. (A triggered ability uses the words “when,” “whenever,” or “at”. Mana abilities can't be targeted.)

When Seafloor Casket enters and when you sacrifice it, target player mills two cards.
{1}{U}, Sacrifice Seafloor Casket: Draw a card.
Cycling {2} ({2}, Discard this card: Draw a card.)

Flash
{U}, Sacrifice Seal of Approval: Counter target spell unless its controller pays {2}.

{U}, Sacrifice Seal of Insights: Look at the top four cards of your library. Put one into your hand and the rest on the bottom of your library in any order.

Reveal the top five cards of your library. You may put an instant or sorcery card from among them into your hand. Put the rest into your graveyard.

At the beginning of your upkeep, surveil 1. (Look at the top card of your library. You may put that card into your graveyard.)
{2}{U}{U}, Sacrifice Search for a New Land: Draw two cards.

Seaside Skimmer can't be blocked if you've cast a Dragon spell or Adventure spell this turn.

Flying
Instant and sorcery spells you cast cost {1} less to cast.
{2}{U}: Target player mills two cards.

This spell can't be countered.
Draw a card.
Reprise {2}{U} (As you cast an instant or sorcery spell, you may exile one card with reprise from your graveyard and pay its reprise cost. If you do, add its effects to that spell.)

Scry 2, then draw two cards. (Look at the top two cards of your library, then put any number of them on the bottom of your library and the rest on top in any order.)

As Secrets of the Orrery enters, choose fact or fiction.
Foresight — Whenever you draw your second card each turn,
• Fact — Target creature can't be blocked this turn.
• Fiction — You may tap target creature. If you do, put a stun counter on it.

Choose one or more —
• Target player draws two cards.
• Counter target spell.

Whenever a creature you control enters, if it wasn't cast from your hand, you may mill a number of cards equal to its mana value. If you do, you may return a noncreature card milled this way from your graveyard to your hand.

Look at the top two cards of target player's library. Put one of those cards on the bottom of their library and the rest on top.
Fuse (You may cast one or both halves of this card from your hand.)

Take an extra turn after this one. During that extra turn, you may cast spells you own not named See the World from outside the game by tapping an untapped Scout you control in addition to paying their mana costs.
Exile See the World.

Shuffle up to five target cards from your graveyard into your library. 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.

Draw three cards. Then discard two cards unless you discard a land card.

Draw a card.
Whenever Seek Guidance is put into your graveyard from your hand or library, scry 2. (This doesn't include being cast.)

Reveal the top three cards of your library. Put one into your hand and the rest on the bottom of your library in any order.

Scry 2, then draw two cards.
You have no maximum hand size for the rest of the game.

Flash
Flying
When Seeker Amalgam enters, you may counter target spell with mana value less than or equal to the number of Elementals you control.

When Seeker of Communions enters, choose target player. If that player is poisoned, draw a card. Otherwise, that player gets a poison counter.

Flying
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)

Whenever you scry, draw a card.