Alagastar's Rapier

You have a +3 bonus to attack and damage rolls made with this magic weapon

This is a variant on Alagastar's Dream Hammer, which changes form depending on its user. 

Immediately upon attunement, you must make a DC 16 WIS saving throw. Upon a failed save, the user takes 4d8 psychic damage, and your alignment shifts to Good until no longer attuned. On a successful save, you take no damage, and your personality remains. You also gain the following bonuses; +2 Wisdom and +1 Charisma to a maximum of 20, Resistance to Psychic damage, expertise in deception, and advantage on Wisdom Saving throws while attuned. This is permanent as long as you are attuned, though reverts to normal if you unattune.

Psychic Aftershock

When this rapier is thrust, a command word can be spoken to activate this property (or cast Psionically). When activated, a thought version of the wielder separates, traveling up to 60 feet, or until it hits a solid object/creature. All creatures outside of 5 feet must make a DC 14 DEX save. On a success, the attack misses and keeps going. On a fail, the creature must take 1d8 piecing damage. If this is cast while attacking a creature, and the original attack hits, the creature is also hit with 2d6 force damage and knocked 10 feet away. 

This can be cast a number of times equal to your intelligence modifier, and one use is restored per long rest.

If the caster is level 10 or above, they can opt to teleport to the final location of the aftershock. 

Dancing Weapon

You can use a bonus action to toss this magic rapier into the air and speak the command word. When you do so, the sword begins to hover, flies up to 30 feet, and attacks one creature of your choice within 5 feet of it. The rapier uses your attack roll and ability score modifier to damage rolls.
While the rapier hovers, you can use a bonus action to command it to follow a specific target, in which case its movement speed is equal to your own. 
After the hovering rapier attacks for the fourth time, it returns to your hand. If you are not within the same plane at it, it will simply fall to the ground where it is currently hovering. If your hands are occupied, it will return to your side, and fall to the ground. The rapier will stop if it is obstructed by a physical object, though if it passes through any living creature, that creature must make a DC 14 DEX save, or take 3d4 piercing damage. This action has a number of charges equal to your spellcasting modifier (minimum 1) that are recharged after a long rest. 

Alagastar's Chosen:

While attuned to the rapier, there is a strong connection between the wielder and the blade. When another creature attempts to take or wield the sword without the consent of the current owner, the new wielder must take 3d8 Psychic damage and make a DC25 WIS save. If they fail, the sword is dropped and returns to its owner's hand. On a success, they can manage to hold onto the sword for one turn, though must make the save again in consecutive turns, though without the damage.

 
Personality:

Spirit of Kirin Alagastar:

Upon his death, Alagastar's soul was sealed within his enchanted rapier imbuing it with a part of the powers granted to him by Vecna when he had served him. Alagastar's will is to continue feeding off of the dreams of others, though not necessarily by Vecna's will, and it will attempt to influence its user through whispers if not satiated on a regular basis. To do this, the player must either use the magic of the rapier to create nightmares in others and allow the rapier to feed off of it, or sacrifice their own strength. Whoever takes the hit must take a level of exhaustion the next day. If ignored for over a month, or if it comes in contact with items such as the Sword of Kas, the rapier may attempt to take control of the user, forcing them to make another DC 16 WIS save, unless the player opts to allow Alagaster to control them. On a failed save, the user is under Alagastar's (DM) control for a total of 3d4+3 minutes, before the spirit must return to the rapier to regain its energy. On a critical failure, the players alignment shifts during the transition and remains until they remove the attunement. 

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

Notes: Bonus: Magic, Resistance: Psychic, Bonus: Charisma Score, Bonus: Wisdom Score, Advantage: Wisdom Saving Throws, Expertise: Deception, Spell caster who has entered the realm of dreams before., Damage, Combat, Finesse, Vex