At the end of the quest line, you receive a strong axe (if I remember correctly), but it's rather a "nice to have" weapon than a "must have" one.
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You're right, I confused it with another reward. Since it has been a while since my playthrough, I should shut my trap until I'm absolutely sure about the answer to any asked question. Still, I never really used the Tetra Elemental, since there are so many other great accessories. It is pretty useful in certain situations, though, e.g. against that one insanely strong mark (hunt) south of Northdale.