Suomi Mercenaries were huntsmen working for the Scriven prior to Fever Crumb. During the Scriven Uprising, they worked to defend their masters from the uprising Londoners and the Skinner's Guild. However they were unsuccessful, as the Scriven were all but wiped out.
Gideon Crumb was nearly shot by a group of Soumi Mercenaries during the riots in London, but their commanding officer recognized him from his days as Auric Godshawk's lab assistant and let him go. Later, as the tide of the riots began to swing decisively in favor of the Skinners, various mercenary groups in the city began switching sides.
Carn Morvish became acquainted with Auric Godshawk while he was working as a mercenary in London, some years before the downfall of the Scriven. Whether he was a part of the Soumi Mercenaries or some other group is unknown.