She speaks

"Why did you summon me, mortal?" the demon said, with a musical voice. "If you are one of the fools that wants to make love to me, know that you are wasting your time: your kind is only prey to me."

"I intend to challange you for control, demon, and I intend to win." Erik said, preparing to cast the geas.

The demon looked amused. "Is that so? Nobody tried it with me so far." she said. "Many of my sisters told me about mortals that did it with them. Some succeeded, some failed, but it was always so much fun for them."

She examined Erik for a couple of seconds. "I can sense you are a decent spellcaster, mortal." she said. "It will be fun to break you."

Having prepared while the demon talked, Erik was ready to use the geas, the only thing he still needed was to know her name.

"Tell me, demon, how can I call you?" he asked.

The demon giggled. "My name would be unpronounceable to you." she said. "But when I am among your people, I use the name Irina. It will have to suffice."

"It will be enough." he said with a smirk, raising his right toward her and yelling the geas formula: "Eam ligas mihi!", meaning "Bind her to me."