Iggwilv

Natasha the Dark, Hura of Ket, Baba Yaga’s daughter, witch par excellence.... these are just a few of the many names of Iggwilv, better known by some as Tasha, the Witch Queen. Through some miraculous stroke of luck you've managed to get in her good graces, or perhaps you're simply a pawn of hers.... whatever the reason you've been graced with some measure of Tasha's vast knowledge of magic, especially in relation to the lower planes.... and you've been granted a sliver of her powers to do with what you like, or perhaps to server her whims as part of some greater game. 

Expanded Spell List

Iggwilv 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.

Fiend Expanded Spells

Spell Level	Spells
1st	bane, hideous laughter
2nd	levitate, augury
3rd	bestow curse, clairvoyance
4th	polymorph, confusion
5th	planar binding, geas

Lore of the Demonomicon

Starting at 1st level, Tasha has bestowed a fraction of her knowledge on you, giving you a greater understanding of the lower planes, and how to interact with their denizens. She's given you comparably little so that she can see how resourceful you are with a meager boon, and should you prove yourself worthy, perhaps by bartering with other creatures that care little for the interests of one depraved mortal, or dealing with fiends or demons, or simply accruing power via hidden knowledge, she'll grant you more blessings..... your career will be watched with great interest. 

You learn Abyssal and Infernal. If you already know one of the languages that you would otherwise gain from this ability, you can instead choose a different language to learn of the languages available to players, or if you already know both of these languages you can choose two different languages to learn instead from the languages available to players. In addition, you have advantage on any Intelligence check you make relating to the lower planes and fiends, and you have advantage on Charisma checks you make to interact with fiends.

Iggwilv's Conjuration

Starting at 6th level, Tasha has taken greater notice of you, you've lived this long, and wielded a fair amount of powerful magicks, perhaps you're worthy of more.... to keep you interesting, and to see just what you'll do with more power... Tasha bestows upon you a small blessing that allows you to be a much better conjurer, whether that means moving yourself and/or others through space and time, or summoning and binding creatures to fight for you...

When you cast a Warlock spell of the Conjuration School, you can cast it without using any verbal, somatic or material components (including costly material components) an amount of times equal to your proficiency bonus, regaining all expended uses after a long rest.

Arcane Redistribution

Starting at 10th level, Iggwilv realizes that you, poor warlock that you are, can't upcast your spells to higher levels, and you can't prepare spells like a wizard, and she takes pity on you, lending you a bit more of her power to help you use your spells better. This is a rather large boon, letting you cast and learn spells more like the Witch Queen does... 

When you gain access to Mystic Arcanums, you can expend a use of your Mystic Arcanums to up-cast a Warlock Spell you know at the level of the Arcanum, without expending a spell slot. In addition, once per day, during a long rest you can choose one of the warlock spells you know and replace it with another spell from the warlock spell list, which also must be of a level for which you have spell slots.

Tasha's Mastery

Starting at 14th level, Tasha has deemed you worthy of receiving one of her greatest gifts, true mastery of spell-craft, and now you can do things that almost no other spellcasters save for the greatest of masters are capable of. You're suitably amusing, and she simply cannot wait to see what you do with this reckless power.

When gain this ability, you choose two Warlock spells you know, these spells must be of the school of Conjuration and they must be spells that require concentration. You are no longer capable of swapping these spells out on a long rest or when you gain another level in this class. You are now capable of concentrating on both of these spells at the same time.

(For example if you choose summon lesser demons and summon greater demons, you can concentrate on summon lesser demons and summon greater demons at the same time, but this does not mean you can stack two instances of either summon lesser demons or summon greater demons, in order to make use of this feature, you must concentrate on the two different spells you chose for this feature.)

When you would be forced to make a concentration check to maintain concentration on these spells, you make concentration checks independently for each one. 

(For example, if you're concentrating on summon lesser demons and summon greater demons, and you are damaged, you must make a concentration check to maintain concentration on summon lesser demons, and then you must make another concentration check to maintain concentration on summon greater demons)