Sometimes in very rare cases, some slimes mutate as they grow older, developing extreme heat tolerances, and even starting to heat up until their body becomes super heated, glowing just like magma.
Naturally, in such a state they become a danger to others around them, so special welded metal suits is made to absorb some heat radiating from their bodies (Often made by themselves using their own heat to bend iron to their will)
Most "magma type" slimes end up choosing to work in dangerous but well paying jobs that involve dealing with high temperatures, smelting and heavy machinery, which is very important for the construction of the walls around Slop & Slime city that keeps ferals and irradiated beasts out.
Bazuli is one of the 3 known magma type slimes in Slop & Slime City, but unlike the two magma sisters who grew up in the city, she is a traveler from the wasteland, after accidentally burning down part of her village, she was banished for being too dangerous to live there, sending her out to find a new place to live, luckily the CEO of Slop & Slime quickly saw her potential and offered her to work in the iron works of the city, where she now resides to this day.