WARNING SPOILERS AHEAD
In the ending of Infinity Blade 3, the Worker is stabbed in the chest by Siris using the Infinity Blade. However he does not die because he invented the blade and thus it is useless against him. Siris proceeds to insert a device found earlier in the Vault of Tears known as the Redeemer into the Infinity Blade. This causes the Worker to disappear in a flash of blue light.
The Redeemer is the same device used by the Worker to cause Siris to be reborn as a child without any memory of his former self. After the credits, Siris and Isa walk over to a child who is building a sandcastle shaped similarly to the Ark (the Worker's base). The child is presumed to be the reborn Worker.
Interesting to note that before the finale, Siris ask the potions master (Eves I presume ?) to modifiy the Q.I.P of a device. Perhaps he managed to modify the Q.I.P of the Worker after Siris defeated him and caused him to be reborn as a child. The Worker could possess a different personality now with a modified Q.I.P.
The past of Siris as Ausar is still very unclear and unexplained; his connections and rivalry with the Worker.