Most likely he’s a Warden who guarded Marygeoise or Impel down.
@Sentinel has a great theory on it. Idk if he could link it
But it went like there was three Wardens, King the WildFIRE, Shiryu of the RAIN, Magellan something POISON epithet. They balanced each other out Kings fire < Shiryu Rain, but fire checks Magellan’s poison, and Magellan checks Shiryu since they were equal in strength but checked in matchups. There was more to it but we should know in a Kaido flashback
And it makes sense why we will meet each of the wardens in a linear process.
First Magellan, then King, then Shiryu. This way we go from Chaotic Good to Chaotic Neutral to Chaotic Evil in a sense