Well, I'll say during a retreat in the T'au Cluster during a crusade launched by the Velkriege (My army) my Ccommissar and all of his men will be left behind by the Navy when about 3 Manta Missile Destroyers and a bunch of ships fleet in under radar and force the fleet away. (Damn navy, not under the command of the ground >.< )
After this, he'll make a last stand against the new forces. After a gruesome war of attrition and gore of about a year, Rel will surrender to the Greater Good. He will be made a Shas'O after much debate by the Ethereal caste on T'au and will lead a new force into imperial space. When it comes to pass, he will turn on the Tau. He will then be known through-out the Imperium as a hero who survived.
Meh. Assembling my first battlesuit tomorrow. Gonna get the scheme down and set up the back story. God I have too many stories to work on.