Which elite Imperial unit does Iden Versio command?

The elite Imperial unit commanded by Iden Versio is Inferno Squad.

Inferno Squad is an Imperial black-ops team created to handle missions requiring more than ordinary stormtrooper forces. In the 2017 game, Iden leads the squad alongside Gideon Hask and Del Meeko, with Shriv Suurgav becoming associated with the unit after Iden's defection. Their flagship is the Corvus, which serves as a mobile base during the campaign.

The unit first appears in the tie-in novel Battlefront II: Inferno Squad by Christie Golden, published in 2017 before the game. The novel depicts the squad's early missions after the destruction of the first Death Star, including an undercover operation against Saw Gerrera's remaining Partisans. It establishes Iden as the team's commander and develops its members before the game's events.

Inferno Squad is not the same as Havoc Squad or Delta Squad. Those are separate Star Wars military units from other stories and games. Rogue Squadron is also unrelated: it is a Rebel and later New Republic starfighter unit rather than an Imperial special-forces team.