They were responsible for at least three known attacks on St. James, one of which was in London. They have a navy of unknown size of Abyss-capable ships, several of which are thought to be patrolling the Aurellis Continuum’s Brownwater region. They are ‘suited’ with full coverage, strongly suggesting that their native continuum is a harsh environment requiring that level of protection for survival. Further, they have an embedded communication system which works by unknown means. It is removable, it looks like a spiderling, and you may find it where the sun doesn’t shine in a given individual.
Should you be fortunate enough to capture one of their ships, you will have to suborn or otherwise control the consciousness which is its pilot (Ship-child) before going Topside, otherwise it will engage a self-destruct sequence.
Addendum:
Terror is ruled by Queen Valentina, of some unknown relation (daughter?) of Valentinian the Conqueror, who created a long-ago Abyss Empire. Most Abyss-capable ships are from that era of construction, and the materials required to make more have largely been mined out of known Continuua. The tie to St. James relates to someone named Valothian, who is thought to be deceased at this point.