Hullbreaker Horror

Flash
This spell can't be countered.
Whenever you cast a spell, choose up to one —
• Return target spell you don't control to its owner's hand.
• Return target nonland permanent to its owner's hand.

Boreal Druid

Wall of Shards

Defender, flying
Cumulative upkeep—An opponent gains 1 life. (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)

Heidar, Rimewind Master

{2}, {T}: Return target permanent to its owner's hand. Activate only if you control four or more snow permanents.

Boreal Shelf

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

Snow-Covered Forest

Arctic Flats

This land enters tapped.
{T}: Add {G} or {W}.

Dryad of the Ilysian Grove

You may play an additional land on each of your turns.
Lands you control are every basic land type in addition to their other types.

Oracle of Mul Daya

You may play an additional land on each of your turns.
Play with the top card of your library revealed.
You may play lands from the top of your library.