From Destinypedia, the Destiny wiki
Jagi's Host was a fireteam of seven Titan Guardians commanded by Jagi. Their prefered armor was either VISIGOTH Type 0 or VISIGOTH Type 1, and patterned with what looked like a six-pointed star. Their mark is known as the Mark of Jagi's Host, and patterned with a gryphon.
Not much is known about them apart from their march south of the Cosmodrome, to the Caspian Sea, where they disappeared. Their Ghosts came back to the Tower, silent and mute. This happening was disturbing enough that even Holborn's Host, out on Mars, heard of it. The Mark of the Lost Seven was created to commemorate and remember their passing.