A grimslake's tail is covered with suckers that extend long, thin, razor-sharp tendrils to drill into its victim's bones, draining them of marrow. As a swift action, a grimslake can drain marrow from a creature it is grappling or from a helpless creature. The victim can resist this painful attack with a successful DC 18 Fortitude save; otherwise, the creature becomes staggered from the horrific agony for 1 round and takes 1 point of Constitution drain. The save DC is Constitution-based.