I genuinely have no idea what you're talking about, and am having some difficulty even parsing your sentence.
Are you talking about polar bears fighting or trying to eat narwhals? If so, while polar bears are omnivores and will try to eat pretty much anything that will sit still long enough, narwhals are not high on their diet. They're too big to hunt, so they'd have to be a "target of opportunity"- IE, sick or badly injured, as well as being close enough to shore it could be dragged up enough to be able to eat enough of it before it floats away.
But generally speaking, on a day-to-day basis, no, polar bears don't eat or attack narwhals.