When creating your character with the Plasmoid race replace the "Hold Breath" trait with the following:
Voidborn: You don't breathe and you are immune to the negative effects of being in the void outside a Spelljammers bubble. You don't need to eat or drink although you are capable of absorbing substances and suffer the effects from them as normal when you do. You instead derive your sustenance from absorbing the energies of the portal between both halves of Broken World. Every Plasmoid has to travel through the portal at least once every five years.
The Plasmoids are possibly the youngest intelligent race in the Core. They are amorphous oozes with no typical shape, extraordinarily capable of surviving without oxygen. They feed by absorbing the extra-dimensional energies spilling from Broken World's portal while they travel through it. Some scholars claim the Plasmoids are an evolution of the Oozes present on many worlds, however the Plasmoids themselves believe they are created by Sessa when she visited Broken World where they live in the asteroids surrounding both sides of the portal. Their first encounter with another intelligent species came but recently when an expedition of Dwarves began prospecting the mineral rich asteroids home to the Plasmoids. After some initial kerfuffle the races came to an agreement and now both live harmoniously on the asteroids which now house the largest off-world Dwarven mining colony Bainen's Delve. The large amounts of trade running through the colony and the portal have thrust the plasmoids head first into the interstellar community and while rare due to their dependency on the portal's energy for sustenance Plasmoid travelers, adventurers or traders are not unheard of.