The Xth Form is a Job Extend that surpasses the normal bounds of The World's gameplay.
After having his PC data heavily damaged by Corbenik's "Rebirth", Haseo finds himself stranded on the outer fringes of "The World's" systems. He is rescued by Zelkova who brings him to his base, Net Slum Tartarga. There Zelkova uses his skill as a hacker to repair Haseo's PC Body. While recovering, Haseo is approached by his Avatar; Skeith. Skeith accuses him of becoming soft, and prepares to abandon him, but Haseo manages to convince Skeith to stay. With Zelkova's help Skeith integrates himself into Haseo's PC Body, creating his Xth form.
As with the second Job Extend, Xth Form adds a new ability to the player's arsenal. With Xth form, it is possible to dash quickly around the battlefield by double-tapping the Guard button - an ability that can in fact be used with all of Haseo's weapons, however, Haseo's dashing distance is relative to his current weapon equipped (i.e. the distance dashed is shorter with a broadsword or scythe currently equipped, but farther with Dual Guns or dual swords).
An briefly image of Haseo in the Xth Form appears in the ending of the final episode of .hack//Roots, Determination, along with Avatar Skeith in his 1st form, hinting that the path Haseo would walk from now on would lead him to this new destiny, the Xth Form, which holds infinite potential.
Like in the G.U. games, Zelkova modifies Haseo's PC body to create the Xth Form. When Kazumi Data Drains Haseo and steals the Epitaph for Skeith, Haseo is rescued by Zelkova. This Xth Form is slightly different than the one obtained in the G.U. games and TRILOGY. Haseo's Dual Guns have hacking abilities that allow him to utilize the Signs left by Ovan. They can also target and stop an experimental Data Drain fired from a Dummy Morgana Factor, though they lack the power to stop a true Data Drain. Haseo can also fire data bullets called "Freeze Shot" that freezes a person's PC and forces it to crash. It could be assumed that Haseo gained his Lost Weapon in this form, since he's still using a normal scythe when fighting Ovan, while he was seen wielding his Lost Weapon during the last chapter. However, unlike in the games, 'Ticking Death' and 'Shadowy Death' are names for the attacks, not the weapon itself.
This Xth Form doesn't utilize Skeith's 3rd Form, and Haseo cannot summon Skeith due to the fact that he is missing his Epitaph. The main power of this Form seems lie more in true hacking rather than summoning large quantities of power, making it akin to Kite's Twilight Bracelet.
Xth Form here is the result of Haseo's fusion with Atoli after being freed from his B-st Form, which he retains even after the fusion ends. It is portrayed here as being vastly more powerful than it is in the games, possessing power surpassing Ovan's unsealed mode. It displays the ability to fire tremendous blasts of blue energy from its gunbarrels. As in the games, it uses Skeith's third form as its Avatar, though due to changes in the storyline Skeith has not consumed the other Epitaphs as it did in the games. Despite this, perhaps due to containing the full power of two Phases, it can fight on an even level with the AIDA-enhanced Corbenik. Haseo can also generate beam wings identical to those used by Skeith in order to fly and enter spaces outside the game, and further possesses the ability to shatter system barriers, making this the most powerful Xth Form in terms of all-around capabilities.
The form returns in Link. However it is no longer exclusive to Haseo. Tokio's party members gain its use with upgraded equipment and abilities.