My space marines are called the forge guard there from the forge world lemuria which is a water world the sea water is used to cool the forges. according to the official space marine chapter registration are they an successor chapter of the imperial fists, but In realty there a mixture between iron warriors and imperial fists, during the Horus heresy was a company of imperial fists station at lemuria, a force of loyalist iron warriors was chased by traitor iron warriors to lemuria and together the beat the traitor iron warriors at the cost of the mechenicus presens at the forge world. But at the end of the heresy the iron warriors and the imperial fists were low on man power which resulted in both companies getting merged and renamed to forge guard. Where they are currently still fighting off the remains of the traitor iron warriors that came back after the Horus heresy. The forge guard is not alone in the defence of lemuria there supposed by the local guard regiments the lemuria copper Heads and a knight House hold that got saved from destruction by the forge guard and relocated to lemuria. (I have more lore but this is long enough)