He began his blog in an effort to salvage an archive of documents regarding the Fears which had been contributed to him by various sources. He also did this in order to lure Thaddeus River into a trap to enable his own escape from Aqualung and The Cold Boy.
His real name is Archibald Donald Sullivan, Junior. His wife and daughter were assimilated by The Camper, and his son disappeared shortly thereafter. Since the creation of his blog, he has drawn the personal attentions of Aqualung, The Cold Boy, EAT, and an as-of-yet unknown entity which is somehow associated with mirrors.
He is also, apparently, Indisen. He carries a piece of EAT's "essence" within himself, which makes him both more difficult for the Fears to harm - though the details of this resilience are unknown - and a high-value target for all of them.
Bitter and acerbic, Locomotive Breath does not make friends easily. When writing his blog posts, he usually comes across as fairly reserved and calm, no matter how dire the situation, and he was described by Christie Waterman as being completely prepared to attack The Cold Boy with a shotgun despite his knowledge that it would be entirely pointless simply because he would refuse to die without making one last gesture of spite towards the Fears. He doesn't bother with politeness or tact, considering them to be wastes of time.
Locomotive Breath doesn't get along with many people. About the only people who might be described as his friends are Christie Waterman, Phillip, and James. Everyone else just gets raw spite.