Battle on Gue'vesa'rio

custodes escorting an imperium diplomat to attempt to regain partial control over their population on the farsight controlled planets are attacked in a tau orbital station by alpha legion and grey knights. grey knights are convinced by who they think are their fellow companions (alpha legion) that the custodians are committing heresy by even attempting to contact xenos. the tau aid the custodians in a defense against the grey knights and alpha legionnaires due to it being within their airspace