Karin had already had the Kobolds prepare her a room for her summoning efforts. Free of any sort of drafts or other disturbances which might disrupt the binding traps.
The process of preparing the two magic circles and their constituent anchoring diagrams took Karin about 20 minutes in total. She could have spent a few hours on each of them, but Karin was a pro, after all. Let the amateurs fumble around for hours.

Everything was in preparation. The circles were prepared, and her four 'bargaining chips' were in the room with her, bound and gagged.

***

Ten minutes of gestures and incantations later and Karin stood before two Succubi in similar outfits, each one trapped in their respective circles. One was a curvacious - although flat compared to Karin - green haired lass, and the other a much flatter - even when compared to people who were not Karin - pink haired one.

"Unholy shit, check out the rack on this cow!" The green haired one laughed in Abyssal. "Hello little mortal." She purred, this time in common. "Called us here for a bit of fun, then?" The other one added.
"Why don't you erase these silly circles and let us out? We don't bite."
"Not too hard, anyway."
"Unless you ask us to."
"You're pretty. Do you fuck as good as you look?"
"We won't know unless you show us."
"Why don't you come closer so I can get a better look at them?"
"Yeah."

Karin's charms, no doubt to her pleasure, seemed to have the same effect on the two Tanar'ri women as it did on everyone else, their eyes glued firmly to Karin's enormous hooters, even as they purred and enticed her and did their best to get Karin to do something very, very, very stupid.

Still, Karin and Hevisa had... a thing going on. If she could deal with Hevisa, surely she could deal with two Succubi who were far less beautiful than her and, most likely, a lot more stable.