Boreal Shelf

Boreal Shelf enters tapped.
{T}: Add {W} or {U}.

Seton's Desire

Enchant creature
Enchanted creature gets +2/+2.
Threshold — As long as seven or more cards are in your graveyard, all creatures able to block enchanted creature do so.

Mystic Zealot

Threshold — As long as seven or more cards are in your graveyard, Mystic Zealot gets +1/+1 and has flying.

Dark Depths

Dark Depths enters with ten ice counters on it.
{3}: Remove an ice counter from Dark Depths.
When Dark Depths has no ice counters on it, sacrifice it. If you do, create Marit Lage, a legendary 20/20 black Avatar creature token with flying and indestructible.

Arcum Dagsson

{T}: Target artifact creature's controller sacrifices it. That player may search their library for a noncreature artifact card, put it onto the battlefield, then shuffle.

Peregrine Drake

Flying
When Peregrine Drake enters, untap up to five lands.

Mystic Enforcer

Protection from black
Threshold — As long as seven or more cards are in your graveyard, Mystic Enforcer gets +3/+3 and has flying.

Treva's Ruins

When Treva's Ruins enters, sacrifice it unless you return a non-Lair land you control to its owner's hand.
{T}: Add {G}, {W}, or {U}.