Have

Lingering Souls

Create two 1/1 white Spirit creature tokens with flying.
Flashback {1}{B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Time of Need

Search your library for a legendary creature card, reveal it, put it into your hand, then shuffle.

Serum Visions

Hangarback Walker

Hangarback Walker enters the battlefield with X +1/+1 counters on it.
When Hangarback Walker dies, create a 1/1 colorless Thopter artifact creature token with flying for each +1/+1 counter on Hangarback Walker.
{1}, {T}: Put a +1/+1 counter on Hangarback Walker.

Insectile Aberration

Delver of Secrets

At the beginning of your upkeep, look at the top card of your library. You may reveal that card. If an instant or sorcery card is revealed this way, transform Delver of Secrets.

Delver of Secrets // Insectile Aberration

Dovin, Hand of Control

Artifact, instant, and sorcery spells your opponents cast cost {1} more to cast.
−1: Until your next turn, prevent all damage that would be dealt to and dealt by target permanent an opponent controls.

Atraxa, Praetors' Voice

Flying, vigilance, deathtouch, lifelink
At the beginning of your end step, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Negate

Raff Capashen, Ship's Mage

Flash
Flying
You may cast historic spells as though they had flash. (Artifacts, legendaries, and Sagas are historic.)

Doom Blade

Putrefy

Destroy target artifact or creature. It can't be regenerated.

Merciless Eviction

Choose one —
• Exile all artifacts.
• Exile all creatures.
• Exile all enchantments.
• Exile all planeswalkers.