At the metagame level: Othar may think he's supposed to kill the Sparks, but the fact is that killing isn't his karma. Therefore, any time that you have someone completely caught, and you could kill them, it doesn't happen. Roleplay this however you like, and feel free to embroider outrageously, and enlist a GM occasionally if it seems appropriate. Sometimes you simply talk until they surprise you and overwhelm you; sometimes you trip and knock yourself out with your own weapon; sometimes a giant Clank comes out of the woods and attacks you at just the moment when you were going to pull the trigger. But something always prevents it.
Characters In Game: Othar
All Characters: Othar
The following are notes made while this was in development. They do not necessarily represent the current state of this ability.
While Othar's theoretical calling in life is to kill all Sparks, there is one little problem: he is fundamentally unable to kill anyone. It's a deep psychological block stemming from childhood, which he does not consciously recognize. But he always subconsciously arranges things so that he never quite gets to kill anyone: either he talks too long, or he makes a mistake, or some such.
This should mainly be played at the metagame level. Othar is very good at playing the hero (in his own eyes), and will tend to win when he's acting as the good guy. But when he is in a position where he might wind up killing another person, he should always find a way to lose, whether by getting out-fenced, or tripping over something, or telling stories for too long, or whatever. He is the avatar of The Villain Who Can't Win, because the killer role just isn't karmically his.