Resurrected by The Timelord War Council during The Height of The LAST GREAT TIME WAR, The Master was given a new Battle Tardis, a new body- and an emergency regeneration (with a promised set of Thirteen granted upon the completion of specific missions)
THE MASTER IS ARMED WITH A LASER SCREWDRIVER. One he constructed shortly after being revived. Using parts harvested from a Sonic Screwdriver, and fused with his tissue compression generator- The Laser Screwdriver could fire a high-powered ray of deadly energy, compress targets into miniature-sized forms (this process was lethal), and age people to death. Along with this, it was armed with the typical components The Sonic Screwdriver had- allowing him to hack and lockpick doors, as well as scan things. Extending the Barrel increased the power of the selected mode.
THE MASTER IS PAIRED WITH ARLECCHINO, The Fourth Harbinger ( @lunaetis ) As well as given a new Battle Tardis. As an experiment, The Timelord war council preprogrammed The Master's Chameleon circuit (in an attempt to see if more races would be receptive to timelord interference if they thought The Master- who... was intended to be a timelord agent was The Doctor.) Into the shape of a faulty Police Box- meaning That The Master is unintentionally impersonating The Doctor.
The Master was able to learn about Teyvat through Arlecchino, who filled him in on the history and mechanics of her home planet (as The Doctor discovered it whilst The Master was dead.) When he was assigned his mission to terminate The Doctor (who was stranded in a parallel universe) he visited The Alternate Teyvat numerous times, disrupting its history.