Gideon possesses the Darksaber. He's only been in a few episodes in The Mandalorian season 2, and one of his previous appearances teased the formation of a Dark Trooper army.
The concept of Dark Troopers is something that Star Wars Legends materials explored, but their arrival in The Mandalorian season 2, episode 4 was their first appearance in canon. Gideon deployed four of the Dark Troopers upon Tython near the end of episode 6, "The Tragedy." They landed on the planet to secure Baby Yoda after communing with the Force while Din Djarin (Pedro Pascal) was preoccupied with regular stormtroopers. After the quick and unclear look at them in the past, their arrival here confirms that they are advanced droids that can fly and likely have great combat skills.
These Dark Troopers are only seen on screen for what amounts to less than a minute, but some might be underwhelmed by their reveal. Droid armies have been done several times in the past and it appeared The Mandalorian was setting the Dark Troopers up for much more. At one point in Legends, a team of Dark Troopers was assembled and all had dark side Force powers. The Mandalorian has established that Gideon is interested in Baby Yoda because of his high midi-chlorian count. He already conducted experiments using Grogu's blood, and the testing tubes indicated Gideon is trying to find a way to give Force powers to anyone he wants - potentially even himself. That goal fits perfectly with the Legends idea that the Dark Troopers had Force powers and would've given Gideon an army of Force wielders at his disposal.
Although some Dark Troopers eventually had Force powers, that wasn't the original plan for them. There were four main versions of the Dark Troopers in Legends, not including the iteration that eventually had Force abilities. At first, they were recycled clone troopers who had roughly 70% of their bodies replaced with cybernetic implants. The next phase of Dark Troopers were droids, but they had some enhancements not yet confirmed to be included with The Mandalorian's versions. They were made of materials that were lightsaber-resistant and had vibro blade and shield attachments. Another phase of these droids increased their firepower and gave them jump packs. A final and third version was designed to be heavy-duty suits for actual soldiers.
As evidenced by the history that the Dark Troopers had in Legends, there is still the chance that The Mandalorian can evolve its own version of them. We've only seen them used for a snatch and grab mission, so they could even have deployable vibro blades. While the current droid builds won't be able to use the Force, it is possible Gideon has the plan to make a line of Dark Troopers with actual soldiers. He's been full of surprises so far, so there's no telling what Gideon's master plan for the Dark Troopers in The Mandalorian might entail.