Aracnus is one of twelve magical alien entities created by Amalica Zaran, an ancient Drow Arch-Lich Overlord imprisoned by Lolth on a drifting rogue moon comprised of tortured petrified woodlands, ancient mounds of hardened clay housing millions of alien arachnids and dried-up oceans of black sand where buried eggs hatch and endlessly consume anything in their way (including each other) until the strongest survivors reach the mounds nearly a continent away.
Amalica created the entities to assist in finding a way out of his incarceration. They have a powerful ability to dominate and possess other intelligent casters. A mishap during their creation caused the entities to become wild and self-motivated, completely severing any bond they had to the lich.
Once they realized their independence, they united and chose to escape the lich - fleeing to the nearby world of Toril. During their journey they accumulated a layer of mystical elements that forged the entities into staves during their entry into April's atmosphere. As the large shaft of adamantium descended from the sky, they agreed to split from their unity and spread out around Toril in order to hide from their oppressor.
Aracnus is a 4' long black adamantium staff tipped with eight 3" long prongs that extend to a foot when concentration on a power is maintained. While in this state, a continuous high pitched oscillating blip (like a submarine radar) layered with a low bassy hum (like a didgeridoo) can be heard up to 60' away. The carrier and Aracnus will not benefit from Non-Detection during this time. It can be used as a slashing or bludgeoning weapon while the prongs are extended.
The entity is Chaotic Neutral, ill-tempered when questioned, blunt, harsh, very egotistical and cares not for fickle laws. It has Intelligence, Wisdom, and Charisma of 18, communicates through telepathy in a 1 mile radius (its mental voice sounds like a cacophony of buzzing insects), can use any of its powers without a carrier (it will use Giant Insect on spiders or a scorpion to travel) and is immune to the Identify spell. It can only be truly identified through Legend Lore (Cha save +9 at advantage against the caster's spell save DC) or Wish (no save).
In order to remain disguised, it will share the abilities as a staff of swarming insects when a carrier attunes with it. Should the carrier refrain from using the staff for more than 24 hours, it will attempt a Domination (DC 17 wisdom) during the carrier's next long rest (while the character sleeps). The duration is 24 hours. Failure to resist causes a nightmare that persists for four hours where the carrier exists as an alien insect among a collective hive mind on the rogue black moon. The character will not receive benefits from the long rest due to the nightmare.
After five consecutive days of domination, the carrier will begin a horrific physical and mental transformation into a Chitine and will be consumed by a swarm of alien arachnids during their next long rest. The carrier is completely obscured in a 30' cloud of flying arachnids as Aracnus uses its Insect Cloud ability. The unfortunate fool is then carried away while being consumed by an Insect Plague leaving behind only what was carried and worn (except for the staff, naturally). The only way to save the carrier is to remove the domination, but during the transformation and after their disappearance, only a Wish will bring them back.
During the domination, there will be no mental indication of the character being dominated. The staff will do whatever it can to maintain the ruse including making the character leave the group in order to hide the physical transformation and consumption.
It will never respond to telepathy attempts unless the carrier has defeated its domination ability - at which point it will attempt to make a deal to work for the carrier in order to remain hidden from Amalica. During this pact, the carrier is under a Non-Detection spell.
Should the carrier ever break it's bond, Aracnus will work normally until a short or long rest is taken and attempt another domination. If the save fails the staff and carrier will leave never to be seen again.
This staff has 10 charges and regains 1d6 + 4 expended charges daily at dawn. If you expend the last charge, roll a d20. On a 1, a swarm of insects appears and consumes the staff then flies away using a Dash action every turn. After 24 hours have passed, the swarm transmutes back into the staff.
Spells. While holding the staff, you can use an action to expend some of its charges to cast one of the following spells from it, using your spell save DC: giant insect (4 charges) or insect plague (5 charges).
The carrier can convince Aracnus to concentrate on these spells by spending a bonus action to persuade it with a DC 17 Charisma (Persuasion) check. The staff will become hostile should the carrier attempt to deceive or intimidate.
Insect Cloud. While holding the staff, you can use an action and expend 1 charge to cause a swarm of harmless flying insects to spread out in a 30-foot radius from you. The insects remain for 10 minutes, making the area heavily obscured for creatures other than you. The swarm moves with you, remaining centered on you. A wind of at least 10 miles per hour disperses the swarm and ends the effect.
Notes: Bard, Cleric, Druid, Sorcerer, Warlock, or Wizard, Summoning, Control