The Varangians, as a force of Latin bodyguards in the Empire, were basically destroyed by the sack of Constantinople in 1204 during the 4th crusade.

There are references to Varangians as a group of some sort as late as 1404 (The Late Byzantine Army, M. Bartusis pg 275) but I'm not aware of any mention of them later, let alone evidence of military actions in the fall.