1what a lava rod buys you
This is one of the better returns on setting up lava fishing in Hardmode. It is a spear despite the name, and it has a stubby reach that punishes anyone hoping to poke from safety.
the embers do the work
Each thrust coughs out a few burning fragments that arc downward, punch through a couple of targets, then sit on the floor for a second or two still dealing damage. Fighting in a corridor or on a flat arena floor keeps them where enemies walk. Fighting over water throws them away, since any liquid kills them on contact.
why it crits so often
Its base critical rate starts far above any other melee weapon, which changes how you build around it. Critical strike accessories and a Godly or Demonic reforge compound on top of an already high floor, so the weapon punches well past what its listed damage suggests.