Final Curse
Instant
Destroy target creature. Each of its controller's opponents loses life equal to its toughness.
The king of the shrouded wastes keeps no bodyguards, for all know the penalty of regicide.

Stutterfly Swarm
Instant
Create two 1/1 blue insect creature tokens with flying and "Sacrifice this creature: counter target spell unless its controller pays ."
Tower protocol #271: windows must be closed at all times.
-Pellium, Archmagus of the Isles

Oszar's Impostor
Creature - Shapeshifter
You may have Oszar's Impostor enter the battlefield as a copy of any creature on the battlefield or any creature card in a graveyard.
"You know, I like this version of you a lot better."
-Oszar, Citadel Counsel

Kirotas, Souls' Balance
Legendary Creature - Spirit Cleric
At the beginning of your end step, each player who controls more than three creatures sacrifices a creature, and each player who controls fewer than three creatures may return a creature from their graveyard to the battlefield.
6/6
To the downtrodden, he is miraculous hope. To the upright, he is inevitable horror.

Temper Charm
Instant
Choose one -
-Blazing Charm deals X damage to target creature
-Discard your hand, then draw X cards
-Destroy target artifact with mana value X

Whimsy Charm
Instant
Choose one -
-Counter target noncreature spell unless its controller pays X
-Scry X, then draw a card
-Put target attacking or blocking creature with mana value X on top of its owner's library

Fortitude Charm
Instant
Choose one -
-Target creature gets +X/+X until end of turn
-Fortitude Charm deals X damage to target creature with flying
-Destroy target nonland, noncreature permanent with mana value X

THese are pretty neat. IT's tough to find X spells that can fit onto charms, but you appear to have done it.

Temper charm still has "blazing charm" in the text. I love the rummage option though.
I suspect Whimsy charm is the strongest just for the cantrip option. Charms are all about niche options, so throwing a simple cantrip in there as a general use option does wonders for them. Even without something to react to you can be proactive and draw a card.

Unbreakable Will
Instant
Until end of turn, creatures you control gain indestructible, and damage that would reduce your life total below 1 reduces it to 1 instead.

I would loooove "Vilify" to say "Enchanted creature gets -2/-2 and is monstrous."

I can't find the card you're referring to

It was this one:

I don't really like the "monstrous" idea, because it only does anything to like 10 cards with a specific mechanic, and the thing it does (prevent them from monstrifying because the game thinks they already have) doesn't really fit the flavor of the card in the same way that no longer being treated as human by other cards because they aren't seen as such does.

Adventurers!

Outland Guide
Creature - Human Werewolf
Daybound
When Outland Guide enters the battlefield, you may search your library for a basic land card, reveal it, and put it into your hand. If you do, shuffle your library.
2/1
"This land holds many dangers..."
//
Outland Ravager
Creature - Werewolf
Nightbound
4/2
"Many, many dangers..."

Uninspired Bard
Creature - Human Bard
At the beginning of your upkeep, discard a card. If you do, exile the top card of your library, and you may cast that card this turn.
3/3

Mushroomancer
Creature - Gnome Druid
When Mushroomancer enters the battlefield, create a food token.
Sacrifice a food token: target creature gets +1/+1 until end of turn.
2/2
"Toadstools from the forest, my friend?"

More crazy combat math on the mushroom, though no worse than Ursapine

Red can rummage or it can get inspired draw. I get that the higher stats compared to Mad Prophet justify having both drawbacks at once, but I wonder if there’s a way to make this with less risk of card disadvantage

Desecrated Sphinx
Creature - Sphinx Zombie
Flying
Whenever you discard a card, target opponent discards two cards.
4/6

Spirit Leak
Instant
Counter target spell unless its controller pays and 3 life.
"Anyone who says they'd never sacrifice for power has never been in a position where they needed to."
-Yeska, Blood Arcanist

Lucifer the Tempter
Legendary Creature - Angel Demon
Prevent all combat damage that would be dealt to Lucifer the Tempter.
At the beginning of your upkeep, put a +1/+1 counter on target creature. Then, each player loses life equal to the number of +1/+1 counters on creatures they control.
2/2

Netara, Mentor of Cinder
Legendary Creature - Human Cleric
Red spells and permanents you control have deathtouch.
2/3
"Anger, impulse, expression, all can be tainted with malice."

does that only affect red permanents, or is it meant to affect all your permanents? because right now I think it does the latter.

Since Desecrated is sorta Consecrated Sphinx "in reverse" I would like that it also had reversed 6/4 stats despite the fact that black creatures have a slight bend towards being more rear end focused.

whoops, yeah, I should have worded it as "red spells and red permanents you control".

Rotfarm Tender
Creature - Elf Zombie Druid
, Sacrifice a creature: search your library for a land card, reveal it, and put it into your hand, then shuffle your library.
, Sacrifice a land: search your library for a creature card, reveal it, and put it into your hand, then shuffle your library.
1/4