Dungeon Geists

Flying
When Dungeon Geists enters, tap target creature an opponent controls. That creature doesn't untap during its controller's untap step for as long as you control Dungeon Geists.

Hedron Crab

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

Sapphire Medallion

Blue spells you cast cost {1} less to cast.

Temple of Mystery

Temple of Mystery enters tapped.
When Temple of Mystery enters, scry 1.
{T}: Add {G} or {U}.

Temple of Deceit

Temple of Deceit enters tapped.
When Temple of Deceit enters, scry 1.
{T}: Add {U} or {B}.

Diamond Mare

As Diamond Mare enters, choose a color.
Whenever you cast a spell of the chosen color, you gain 1 life.

Maddening Cacophony

Kicker {3}{U}
Each opponent mills eight cards. If this spell was kicked, instead each opponent mills half their library, rounded up.

Hallowed Fountain

({T}: Add {W} or {U}.)
As Hallowed Fountain enters, you may pay 2 life. If you don't, it enters tapped.

Didn't Say Please

Counter target spell. Its controller mills three cards.

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.)

Watery Grave

({T}: Add {U} or {B}.)
As Watery Grave enters, you may pay 2 life. If you don't, it enters tapped.

Rivendell

Rivendell enters tapped unless you control a legendary creature.
{T}: Add {U}.
{1}{U}, {T}: Scry 2. Activate only if you control a legendary creature.

Temple of Epiphany

Temple of Epiphany enters tapped.
When Temple of Epiphany enters, scry 1.
{T}: Add {U} or {R}.

Archive Trap

If an opponent searched their library this turn, you may pay {0} rather than pay this spell's mana cost.
Target opponent mills thirteen cards.

Overwhelmed Apprentice

When Overwhelmed Apprentice enters, each opponent mills two cards. Then you scry 2. (Look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Fraying Sanity

Enchant player
At the beginning of each end step, enchanted player mills X cards, where X is the number of cards put into their graveyard from anywhere this turn.

Traumatize

Target player mills half their library, rounded down.

Temple of Enlightenment

Temple of Enlightenment enters tapped.
When Temple of Enlightenment enters, scry 1.
{T}: Add {W} or {U}.

Island

Otawara, Soaring City

{T}: Add {U}.
Channel — {3}{U}, Discard Otawara, Soaring City: Return target artifact, creature, enchantment, or planeswalker to its owner's hand. This ability costs {1} less to activate for each legendary creature you control.

Unsummon

Return target creature to its owner's hand.

Aegis Turtle

Leyline of Anticipation

If Leyline of Anticipation is in your opening hand, you may begin the game with it on the battlefield.
You may cast spells as though they had flash.

Drowned Secrets

Whenever you cast a blue spell, target player mills two cards.

Bruvac the Grandiloquent

If an opponent would mill one or more cards, they mill twice that many cards instead. (To mill a card, a player puts the top card of their library into their graveyard.)