Borissimo

Aha, I see the issue. Yuriy, what you're missing is the phrase "encounter or evade?" written in the bottom right hand corner of the screen when the Sinspawn first appears. If you use the caltrops then, then you'll only evade the monster. You have to encounter the monster, then use caltrops to defeat it -- which means that, for the Sinspawn, you need to make that dang wisdom 6 check.