Mythril Halberd

Hold the button and it stabs on a fixed rhythm, out and back. The shaft hurts on the way back as well as the way out, so the technique is to stand at the edge of your reach and let things walk onto it rather than chasing them. Against worms and other segmented enemies a single stab lands several times.

It is a holding weapon. Corridors, doorways, the mouth of an arena during an event. In open space against something fast it loses to a swung sword, because you cannot cover angles with it and you cannot reposition mid stab.

Which of the two halberds your world offers is decided at world generation. The Orichalcum Halberd fills the same slot at the same point in the game, so there is no reason to go chasing the other ore for it.