Setesh does this when the 2 renegades with higher initiative have acted, and assuming there are a few renegades within firing arc of his flamer where Verateka or her minions are included (I imagine servitor and Verateka+hound is on two different flanks of the larger group of renegades, so Setesh would fire in the middle kinda). Added reaction to servitor shooting at Setesh.
Setesh sighed, unheard by anyone. "++What a bother.++" he replied, the heretek's reluctance to hurt her own malfunctioning servitor making the situation harder than necessary. "++I cannot promise how long I can ignore it shooting that plasma cannon at me heretek.++" Setesh expertly drew and lined up his flamer to quickly deal with the renegades, trying to get as many of them as possible within the gout of flames, while avoiding the servitor, the heretek and her mechanical hound. "I suggest standing down and submitting yourselves as my sacrificial slaves if you do not want to taste more burning promethium."
After Setesh had launched his flames at the renegades, he quickly maneuvered to cover as to protect himself from the plasma blast which would probably come again as he now was a target.
Half Action shoot flamer.
Those within the 20m range, 30 degree arc cone-shaped area of flames need to test Agility or be struck with (1d10+9) damage, Pen 4.
If they take damage they need to test Agility or be set on fire. Cover only helps if they are entirely in cover, which I don't think they are if they've been shooting at the servitor.
Half Action move to heaviest cover available within 11 meters.