The Z Sword is a weapon of legend, said to be able to grant a power over it's wieldier far beyond their imagination should they be able to draw it. You gain a +3 bonus to attack and damage rolls made with this magic weapon. Unlike the usual weapon,  this one requires two creatures to attune to use it's full power. While free from it's containment, it grants those attuned to it the following properties:

 Bonded Pair: The unique two creature attunement for this item allows them to work as one; While you are mounted on your partner, you may choose which paired creature is affected by effects that normally target only one of you. Your turns become one singular turn, allowing you to move and attack at the same time. 

Time Snatch Aura: Your paladin aura gains an additional effect: Mounted creatures and their riders are immune to the influence of time magic if they so choose; any ability that would modify the roll value of an attack roll, saving throw, skill check, or other circumstance where you can roll a die (portent, convergent future, ect) allows you to choose which die or option is used, as if the ability was your own. In addition, time cannot stop inside the area of this aura, unless allowed.

Time Drain: Once per turn, when you deal radiant damage to a creature, you may drain some of their time; their natural life span is reduced by an amount of hours equal to the radiant damage dealt. In addition, their charisma score is reduced by 2d4. A creature who's charisma is reduced to 0 this way is suspended in time; time is stopped for them, until a greater restoration spell or higher is used to restore at least 1 point of charisma.

Rebel's Warbanner: Your valkyrie banner becomes more flexible; when you place down your banner, you may make a second banner upon your back that follows with you, in addition to the placed one. When you use the Commander's Strike feature while inside your banner, the creature may first move up to it's movement speed before attacking. While inside this banner, the duration of negative effects on friendly creatures is 1 round less. If a hostile creature enters within your banner's reach, it must make a charisma saving throw versus your spell save DC. On a failure, they take a number of d6s in radiant damage equal to amount they rolled on their save, or half as much on a success. 

 Change the Future: The blade's powers over time allow you to affect the timestream a significant amount; allowing you to release a signature attack of powerful energy on even the mightiest of foes. As an action, you may creature a dome of energy that lasts until the end of your next turn with a 30ft radius centered on you, that fires up in a 15ft wide beam into the air. Creatures caught in the area of this attack are caught in the time stream, being launched into one of two realities. Creatures caught make a charisma saving throw based on your spell save DC. On a failure, they take radiant damage equal to both attuned creatures combined hit points, and are flung into the past. On a success, they take no damage, and are flung into the future. to determine how far they travel, roll 1d100. On a 1-10, they travel one minute. on a 11-30, they travel back one hour. On a 31-60, they travel back 10 hours. and on a 61-90, they travel a number of days equal to the amount rolled. And on a 91-99, they travel a number of years equal to the amount rolled. Finally, on a 100, they travel for 1000 years. Creatures sent to the future this way do not exist until it is their time to return. then they appear in the same space they left, as if no time had passed at all. Creatures sent to the past this way re-experience whatever time is traveled, until they hit the point where they were banished again. From others' point of view, it would be as if they were banished for X amount of time, and then returned. Once you use this ability, you cannot use it again until you take a long rest.

 Sky Dragon: Your valkeric abilities can modify your mount even more; allowing you to change it's stat block to be older or younger with your channel divinity. When doing this, you can also choose sizes up to gargantuan+, as long as the creature can fit in it's current space. The mount itself gains a number of benefits as a result of this newfound latent potential it unlocks; it's maximum hit points are doubled, and it gains a new attack, and a new passive ability: Royal Judgment. When a hostile creature you can see rolls initiative, you automatically fire a powerful Thunderforce Attack attack at it, destroying weaker creatures and wounding more powerful ones. Thunderforce Attack (60ft): Creatures hit must make a DC 20 Constitution saving throw (Creatures CR/Level 10 and lower fail automatically). On a failure, a creature drops to 0 hit points. On a success, a creature takes 39 (13d6) Radiant damage. A creature who takes on these transformations gains an air of divinity, and the creature type "Divine-Beast", along with it's normal type.

Bound Sword: Although the sword itself is bound, bound deeper within it is an elder, who's age is immemorial. The elder's sentience is described below. 

Sentience

The Z Sword is a sentient weapon of Neutral alignment, with an Intelligence of 26, a Wisdom of 6, and a Charisma of 10. It has hearing and blindsight out to a range of 120 feet, although it may not choose to use this to your advantage, and expertise in history and nature checks. The weapon communicates verbally with its wielder and can speak, read, and understand Celestial and Abyssal. The elder within has the ability to recall information about a large variety of places and realms due to his long life: he may choose to make history checks to recall this information at his leisure.  

Personality

The elder is motivated mostly by beautiful women, locales and art. He enjoys anything that looks nice, and is more willing to help if given such things regularly. He also wishes to be free of the sword by shattering it, but what happens in that event is unknown.

The Elder harbors a secret doubt about his own Purpose. He fears he has forgotten why the Z sword exists to begin with

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

Notes: Bonus: Magic, Valkyrie, along with their bonded partner, Damage, Buff, Utility, Combat, Sentient, Versatile, Sap