Fiend's Warrior

She draws her blade as she cuts down an enemy. Then, her weapon shifts into crossbow and she shoots the zombie in the head. A half-second later the zombie bursts into flame. She stops for a moment to catch her breath, a raspy voice laughing manically in her head. She knows the deal, she knows what must be done.

He stops running for moment bow at the ready. He can hear them skittering and sliding through walls. He hopes he can see his friends again in this dark dungeon. With resigned sigh, his form shifts as he grows horns and the air becomes a little hotter. His weapon shifts into his beloved greatsword as he walks into the dark room.

These people are what are known as the Fiend's Warriors. Somehow, they found a fiend and struck a deal with them, enhancing their martial capabilities. They don't number in the many, but they do number in the powerful. Wielding magic as well their weapon, they fight on borrowed power and learned brutality. 

Pact Magic

When you reach 3rd level, you can augment your combat techniques with the ability to cast spells. See chapter 10 of the PHB for the general rules of spellcasting and chapter 11 of the Player’s Handbook for the Warlock spell list.

Cantrips. You learn two cantrips of your choice from the warlock spell list. You learn an additional warlock cantrip of your choice at 10th level.

Spell Slots. The Fiend's Warrior Spellcasting table shows how many spell slots you have. The table also shows what the level of those slots is; all of your spell slots are the same level. To cast one of your warlock spells of 1st level or higher, you must expend a spell slot. You regain all expended spell slots when you finish a short or long rest.

For example, when you are 8th level, you have two 2nd-level spell slots. To cast the 1st-level spell witch bolt, you must spend one of those slots, and you cast it as a 2nd-level spell.

Spells Known of 1st Level and Higher. At 3rd level, you know two 1st-level spells of your choice from the warlock spell list.

The Spells Known column of the Fiend's Warrior table shows when you learn more warlock spells of your choice of 1st level and higher. A spell you choose must be of a level no higher than what’s shown in the table’s Slot Level column for your level. When you reach 11th level, for example, you learn a new warlock spell, which can be 1st, 2nd, or 3rd level.

Additionally, when you gain a level in this class and order, 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.

Spellcasting Ability. Charisma is your spellcasting ability for your warlock spells, so you use your Intelligence whenever a spell refers to your spellcasting ability. In addition, you use your Charisma modifier when setting the saving throw DC for a warlock spell you cast and when making an attack roll with one.

Spell save DC = 8 + your proficiency bonus + your Charisma modifier

Spell attack modifier = your proficiency bonus + your Charisma modifier

FIEND'S WARRIOR LEVEL	CANTRIPS KNOWN	SPELLS KNOWN	SPELL SLOTS	SLOT LEVEL
3rd	2	2	1	1st
4th	2	2	1	1st
5th	2	3	1	1st
6th	2	3	2	1st
7th	2	4	2	2nd
8th	2	4	2	2nd
9th	2	5	2	2nd
10th	3	5	2	2nd
11th	3	6	2	2nd
12th	3	6	2	2nd
13th	3	7	2	3rd
14th	3	7	2	3rd
15th	3	8	2	3rd
16th	3	8	2	3rd
17th	3	9	2	3rd
18th	3	9	2	3rd
19th	3	10	2	4th
20th	3	11	2	4th

Formless Weapon

Also at 3rd, you can spend 1 hour, while touching two weapons of your choice, and combine two weapons of your choice (the weapon cannot be a Firearm ). As a bonus action, you can switch to the other weapon's form.

Also, if you are disarmed or don't have the weapons of this feature equipped, you can summon the weapon in any form as a bonus action as long as it is on the same plane as you.

Eldritch Smite

At 7th level once per turn on one of your attacks, you can call upon the power of your patron. You can expend one of your spell slots and deal an extra 1d8 of fire damage. The damage increases by 1d8 every level of the spell slot above 2nd.

Eldritch Surge

At 10th level when you use your action surge feature, you can use the other slot of your Eldritch Smite feature on your turn.

Eldritch Calm

At 15th level when you cast a spell that requires a saving throw, you can spend a use of your Indomitable feature to impose disadvantage on the saving throws of the spell.

Otherworldly Form

At 18th level on your turn, you assume a form slightly resembling your patron. While in this form you gain the following effects:

• You have advantage on all saving throws against magical and spell effects.
• You gain resistance against slashing, bludgeon, and piercing damage.
• Your attacks now deal additional fire damage equal to your Charisma modifier.

This form last 1 minute. Once you assume this form, you can't use it again until you finish a long rest.