The Spire is not a separate nation state in and of itself, it is more like a city-state that enjoys an implicit neutrality between the major powers. Why? Because even powerful nations like Frisia and Iberia require somewhere to trade and bargain where prying eyes will not see them and the contraints of diplomacy and courtly manners do not apply. The Spire is that place!
As a result, the Spire has gained a reputation as a haven for pirates, rebels, privateers, the lost, the dispossessed and the heretical. Administered by the mysterious Lady of Masks, there are no restrictions on who can visit, trade or settle the Spire, as long as they follow her rules.
Marot - a leader of thieves and vagabonds in the warehousing district
Whilst the Lady of Masks holds control of the Spire, she does so with the compliance of the pirate and privateer captains that call the place home. The rules of the Spire mandate that if a major decision is to be made, the Lady of Masks should consult the Council of Captains - a gathering of all the men recognised as Captains of a Fighting Ship currently docked at the Spire. As such, the Council varies massively in its balance and demeanour, but it holds true to the nature of the Spire