Loki looked at her hand. He had a few options. He could pull out a hidden blade and stab her hand. He could use some form of magic to blind her at least for a moment. He could just lie to her, that was always an option... And lastly, he could accept the handshake. Speak to her. Whatever would his brother say if he knew that he had confided in Natasha? Would he be proud? Would he question his motives? If Loki, for one moment, laid himself vulnerable to this woman, would he only leave himself open to become something worse should anyone accuse him of getting up to his old tricks? He was who he was, there was very little changing that.
"We have a deal..." he said eventually, taking her hand and shaking it. He kept a hold of her hand, gripping a little tighter. "However, if you do go back on your word, and if any one else hears of this, I will not hold back..." he warned. He had been holding back since he arrived in Preya. That post of his was just his way of having some fun, scaring some people a little, seeing how they would react.
He waited for her response. Inside his mind, everything that happened played out. He wanted her to give him a reason to hold back, to turn back to his old ways. And he hoped that she was not about to fool him again...