Fraying Omnipotence

Each player loses half their life, then discards half the cards in their hand, then sacrifices half the creatures they control of their choice. Round up each time.

Bitterheart Witch

Deathtouch
When Bitterheart Witch dies, you may search your library for a Curse card, put it onto the battlefield attached to target player, then shuffle.

Festering Newt

When Festering Newt dies, target creature an opponent controls gets -1/-1 until end of turn. That creature gets -4/-4 instead if you control a creature named Bogbrew Witch.

Infectious Curse

Enchant player
Spells you cast that target enchanted player cost {1} less to cast.
At the beginning of enchanted player's upkeep, that player loses 1 life and you gain 1 life.

Accursed Witch

Spells your opponents cast that target Accursed Witch cost {1} less to cast.
When Accursed Witch dies, return it to the battlefield transformed under your control attached to target opponent.

Accursed Witch // Infectious Curse

Baba Lysaga, Night Witch

{T}, Sacrifice up to three permanents: If there were three or more card types among the sacrificed permanents, each opponent loses 3 life, you gain 3 life, and you draw three cards.

Raving Dead

Deathtouch
At the beginning of combat on your turn, choose an opponent at random. Raving Dead attacks that player this combat if able.
Whenever Raving Dead deals combat damage to a player, that player loses half their life, rounded down.

Bogbrew Witch

{2}, {T}: Search your library for a card named Festering Newt or Bubbling Cauldron, put it onto the battlefield tapped, then shuffle.

Warlock Class

(Gain the next level as a sorcery to add its ability.)
At the beginning of your end step, if a creature died this turn, each opponent loses 1 life.
{1}{B}: Level 2
When this Class becomes level 2, look at the top three cards of your library. Put one of them into your hand and the rest into your graveyard.
{6}{B}: Level 3
At the beginning of your end step, each opponent loses life equal to the life they lost this turn. (Damage causes loss of life.)

Bog Witch

Grievous Wound

Enchant player
Enchanted player can't gain life.
Whenever enchanted player is dealt damage, they lose half their life, rounded up.

Candlegrove Witch

Coven — At the beginning of combat on your turn, if you control three or more creatures with different powers, Candlegrove Witch gains flying until end of turn.

Caligo Skin-Witch

Kicker {3}{B} (You may pay an additional {3}{B} as you cast this spell.)
When Caligo Skin-Witch enters, if it was kicked, each opponent discards two cards.