Last chapter, one of the punks mentioned that a person's experiences might also be in their lineage factor. So, the way Poseidon just re emerges from mermaids might be like that. The of Poseidons genes get passed down. And when it's the right time, it activates.
Yeah that's what I was thinking. Pluton can be build, a ship described as out of this world and nearly impossible to build, then similar logic with Poseidon weapon, genes passed down on generation like let's say every 100 years a new mermaid with might get born with a chance to activate the poseidon genes.
Maybe Uranus could be mind controlled. Like let's say an object, or Imu's crown, or a ring let's him connect with the weapon and control it via his mind. Would be interesting if one of the 6 "Moons" is Uranus, and he connects to it via said object. Death star.