Soulcoil Viper

{B}, {T}, Sacrifice Soulcoil Viper: Return target creature card from your graveyard to the battlefield with a finality counter on it. Activate only as a sorcery. (If a creature with a finality counter on it would die, exile it instead.)

Anoint with Affliction

Exile target creature if it has mana value 3 or less.
Corrupted — Exile that creature instead if its controller has three or more poison counters.

Offer Immortality

Target creature gains deathtouch and indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Bonepicker Skirge

Flying
Corrupted — As long as an opponent has three or more poison counters, Bonepicker Skirge has deathtouch and lifelink.

Swamp

Braids's Frightful Return

Read ahead (Choose a chapter and start with that many lore counters. Add one after your draw step. Skipped chapters don't trigger. Sacrifice after III.)
I — You may sacrifice a creature. If you do, each opponent discards a card.
II — Return target creature card from your graveyard to your hand.
III — Target opponent may sacrifice a nonland, nontoken permanent. If they don't, they lose 2 life and you draw a card.

Ravenous Necrotitan

Corrupted — When Ravenous Necrotitan enters, sacrifice a creature unless an opponent has three or more poison counters.

Not Dead After All

Until end of turn, target creature you control gains "When this creature dies, return it to the battlefield tapped under its owner's control, then create a Wicked Role token attached to it." (Enchanted creature gets +1/+1. When this Aura is put into a graveyard, each opponent loses 1 life.)

Pestilent Syphoner

Flying
Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)

Prosthetic Injector

Equipped creature gets +0/+2 and has toxic 1. (Players dealt combat damage by equipped creature also get a poison counter.)
Equip {1}

Thornplate Intimidator

Offspring {3} (You may pay an additional {3} as you cast this spell. If you do, when this creature enters, create a 1/1 token copy of it.)
When this creature enters, target opponent loses 3 life unless they sacrifice a nonland permanent or discard a card.

Duress

Target opponent reveals their hand. You choose a noncreature, nonland card from it. That player discards that card.

Scheming Aspirant

Whenever you proliferate, each opponent loses 2 life and you gain 2 life.

Gulping Scraptrap

When Gulping Scraptrap enters or dies, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Hidden Necropolis

Hidden Necropolis enters tapped.
{T}: Add {B}.
{4}{B}, {T}, Sacrifice Hidden Necropolis: Discover 4. Activate only as a sorcery. (Exile cards from the top of your library until you exile a nonland card with mana value 4 or less. Cast it without paying its mana cost or put it into your hand. Put the rest on the bottom in a random order.)