Slight spin-off of the creature Grendel from the epic poem Beowulf. Basically, a Grundler is the filthiest beast ever imaginable that lurks in your basement. The Grundler is actually an overweight man and has a rancid beard. The Grundler lurks in the shadows waiting for the opportunity to "bag-and-tag" a helpless victim.
1. The boy ventured into the dark basement to find his favorite toy when he was "sacked" by the Grundler and taken away to the Grundler's cave.