Selma, Selene and Arty

"Congratulations Thordak, it seems your goblin has decided to sacrifice herself for you."

• Selene mocks Thordak as she stabs a paralysed Mimsi.

Selma, Selene and Arty were described by Layla in her rings of recording as they arrived in Oar's Rest and stayed with Layla for a week. Notably they only spoke to her twice.
They asked her 'Why does the sun shun the dark?' which elicited a violent reaction from Layla as she punched Selma in a rage. After this, it seemed a small part of Layla snapped and broke out in laughter with the trio before they left.
Days later, Layla found that Selene had been living in the cupboard beneath her stairs for a number of days. When confronting her, Layla noted that Selene said 'They are Pleased' in response to this, Layla stabbed Selene and then they laughed together before Selene left Layla's home with her wound still pouring blood.
Nothing else is known of these three in terms of appearance other than they looked like humans according to Layla but notably shared the same kind of eyes as her.
The siblings arrived on the Mistwalker during the battle in the Sea of Chaos. During that time, they took active joy in assaulting Persicorum and treated the whole experience with playful disinterest.
The siblings seemed to be constructs as, when Baralas and Kodo killed Selene, her innards were composed of silken gears and she bled in very VERY small quantities.
The siblings showed themselves to be powerful spellcasters as well as skilled combatants using a unique weapon called a 'Silken blade' a sharp, whip like roll of cloth that they wield like a blade.
They also seemed to share damage with one another when they were hit.
Their impact on Persicorum:

• Kodo and Baralas managed to destroy Selene in the battle in the Sea of Chaos.
• Arty is responsible for killing Baralas and reducing Gwydion to extremely low health in the battle during the sea of chaos.
• The siblings revealed they wanted to kill the members of Persicorum in order to isolate Olympia.