It's everyone's favorite third-level spell set as a trap. Just touch the trigger and whoosh! Instant barbecue! Sprugtooth keeps a bottle of Famous Dave's Rich and Sassy for afterwards.
Detect: Per-based Thaumatology, or Perception + Magery for mages, at -7.
Circumvent: Automatic (don't trigger).
Effects: 6d burning to the opener and everyone else in a 6-yard radius.