The Oni Sage (Warlock Subclass)

"'In many situations, it is not uncommon for some Oni's to take up slaves as second in command. In these occurrences, these people go through vicious training( maintaining heat in cold, surviving vicious animal attacks, etc.) to meet up to their masters’ expectations. Few survive past their first week of training, but those who do begin to feel an influx of power flow through them, of mystic and lecherous arts. Their skin may discolor, their demeanor, sunken. So it is, that they derive their powers from these monstrous beings of strength and wit.'"

Expanded spell list
The Oni sage lets you choose from an Expanded list of spells when you learn a warlock spell. The following spells are added to the warlock spell list for you.

Bonus proficiency
As an Oni sage warlock, you gain proficiency in medium armor at 1st level.

Martial training
As an Oni sage warlock you are trained in a martial art, and you gain a fighting style of your choice from the fighter or ranger fighting style lists at 1st level.

Chaotic strikes
Your Patron has granted you with empowered strikes with elemental capabilities. At 1st level, when making unarmed attacks, you add your charisma modifier to hit, and you deal bludgeoning damage equal to 1d4 + your strength or dexterity modifier + your charisma modifer. your unarmed attacks count as magical for the purpose of bypassing resistances.

At 6th level, your unarmed damage is increased to 2d4+your strength or dexterity modifier + your charisma modifier and allows you to choose between bludgeoning, piercing, slashing, fire, cold, lightning, thunder, poison, acid or force damage.

Oni’s mind
At 10th level, your mind has been cleared of all distraction, and you can no longer be charmed or frightened. You also gain advantage on wisdom and charisma saves when concernining being controlled.

Seeker of the shadows
You have acquired abilities to lurk in the shadows, moving beyond the points of simple fluidity. At 14th level, you move an extra 15 feet as long as you aren’t wearing medium armor, and any armor that you are proficient in that doesn’t grant disadvantage on stealth check grants advantage on stealth checks instead.