Watery Grave

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

Glasspool Shore

Glasspool Shore enters tapped.
{T}: Add {U}.

You may have Glasspool Mimic enter as a copy of a creature you control, except it's a Shapeshifter Rogue in addition to its other types.

Scry 1. (Look at the top card of your library. You may put that card on the bottom.)
Draw a card.

Target player shuffles their graveyard into their library.
Draw a card.

If an artifact or creature entering causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Return target creature to its owner's hand.
Addendum — If you cast this spell during your main phase, draw a card.

Changeling (This card is every creature type.)
Changeling Outcast can't block and can't be blocked.

Drowned Catacomb enters tapped unless you control an Island or a Swamp.
{T}: Add {U} or {B}.

You may have Jwari Shapeshifter enter as a copy of any Ally creature on the battlefield.

Destroy target creature. You lose 2 life.

Rally — Whenever Kalastria Healer or another Ally you control enters, each opponent loses 1 life and you gain 1 life.

Return target creature to its owner's hand. Its controller draws a card.

{T}, Pay 1 life, Sacrifice Polluted Delta: Search your library for an Island or Swamp card, put it onto the battlefield, then shuffle.