One of Two

Alternate timeline
(covers information from an alternate timeline)

One of Two was a prominent Borg Sentinel who lived during the 24th century.

At some point before 2401, One of Two was killed by General Jean-Luc Picard, and his skull was later mounted on display in his trophy room at Château Picard. (PIC: "Penance")

This Borg drone was only mentioned in writing.
They were previously identified by Dave Blass on Instagram. [1](X)