This staff is made out of adamantine and was forged in the nine hells. It allows the wielder to draw power from the nine hells using their own inner energy. In addition the staff does an additional 1d4 fire damage and 1d4 necrotic damage on a critical hit. Save DC=8+WIS+Proficiency for any ability that requires a save.

The staff is fueled by a creature’s Ki, and if used in excess can corrupt the user’s soul. A creature that uses over half its maximum Ki points to power this staff without taking a long rest is corrupted and shifts alignments 1 step towards Lawful or Evil. A Lawful Evil creature who expends over half its maximum Ki points to power this staff without taking a long rest has been fully corrupted and has effectively sold its soul. You can not use more charges than your Ki point maximum. The staff has 10 charges for the following properties. For each charge expended, you must also spend a Ki point. You regain all charges on a long rest. If all charges are expended roll 1d20, on a 1 the staff disintegrates and deals 10d10 fire and 10d10 necrotic damage to the attuned creature. You may choose to roll a 1.

Hellish Resistance; 1-3 charges

You can spend 1 charge as a bonus action to gain resistance to fire or necrotic damage for 1 minute, or expend 2 charges to gain resistance to both. As a reaction you can spend 3 charges to gain immunity to both until the end of your next turn. You can share this resistance with a number of creatures within 5 feet of you up to your Wisdom modifier by spending an additional charge per creature.

Hellfire; 1-10 charges

Use your action to create a cone of hellfire. Each creature in a 10-foot cone must make a Dexterity saving throw. A creature takes 2 martial arts dice fire and necrotic damage on a failed save, or half as much damage on a successful one. Damage increases by 2 martial arts dice per charge and range increases by 10 feet. You can choose a number of creatures to exclude from this attack up to your wisdom modifier. The fire ignites any flammable objects in the area that aren't being worn or carried. 

The Road to Hell...

A creature can spend 5 charges to plane shift to Avernus. Alternatively, if you know the sigil sequence of a teleportation circle within the hells, this spell can take you to that circle. You can use this spell to banish an unwilling creature to Avernus. Choose a creature within your reach and make a melee spell attack against it. On a hit, the creature must make a Charisma saving throw. If the creature fails this save, it is transported to a random location in Avernus. A creature so transported must find its own way back to your current plane of existence.

The staff also functions as a sending stones with unlimited use as long as you are on the same plane as the bonded fiend and are not on consecrated ground. As part of the pact you agreed to when you attuned to this weapon, you can not willfully part with this weapon or allow the bonded fiend to be harmed. You may end the agreement at anytime by destroying this nearly indestructible staff.

Weapons and ammunition made of or coated with adamantine are unusually effective when used to break objects. Whenever an adamantine weapon or piece of ammunition hits an object, the hit is a critical

 

Proficiency with a Quarterstaff allows you to add your proficiency bonus to the attack roll for any attack you make with it.

Notes: Damage: Fire, Damage: Necrotic, Mark off 1 Ki point for each expended charge, Monk, Communication, Buff, Cursed, Versatile, Topple