Slitherine

Dismounting the Navarrese knights makes them invisible, leaving only the dreaded blue circle.
Pretty cool if you're trying to sneak up on somebody, but not, I suspect, a design-feature as such.
I'd guess either the link or the pic is misspelled Navarese somewhere.

Lars

EDIT: Never mind.
The buggers have re-appeared. Apparently restarting the game helped.
Either that, or there's a time-warp somewhere.

Nah, they knew who they were up against and legged it!