Toriel often sets traps around the ruins near her house to capture monsters and use them as toys during her lonely moments, devouring them, using them as anal plugs, and especially as toys for her penis. Her favorite activity is melting all her prey inside her balls and then ejaculating on them wherever she can.
When humans fall into her traps, her day is made. For Toriel, no other prey struggles with such desire inside her balls as humans do; she loves feeling them melt and leaving her balls full of semen. And for a long time, she has been planning ways to attract more humans to entertain her during her lonely moments.