The Sand Worm is an enormous worm that resides in the sand. It builds a sand trap around it and waits in its center to feed on any unsuspecting preys who happen to fall inside it.
The sand worm from the Egyptian desert of Boku Dracula-kun acts much like its icy counterpart, Rahab, and like other flying dragons from previous games. It can enter and exit a variety of holes in the ground, and comes out floating in looping patterns.
After crossing a Mummy-infested desert near the beginning of Sandy Grave, Jonathan and Charlotte arrive to a big mound of sand. While stepping on it, the ground suddenly splits apart and a giant Sand Worm emerges from the center of what now is clearly revealed to be a sand trap dragging the heroes toward the monster. Once defeated, the worm contorts violently in a shower of blood. If the heroes let themselves get swallowed by the now vacant sand trap, they'll be able to wander its interior, where an HP Max Up can be found. This is actually a tutorial for when the player reaches the Forgotten City, where the main area has to be entered in the same way, by letting the heroes get swallowed by the quicksand, albeit this time after fighting a Poison Worm.
Another Sand Worm awaits at the rightmost wing of Sandy Grave, although this time its lair cannot be entered.
- The Poison Worm is an alternate version of the Sand Worm, both appearing in Castlevania: Portrait of Ruin.
- While other giant worms have previously appeared in the series, the Sand Worm's portrayal in Portrait of Ruin appears to have been inspired by the Sarlacc pit monster from the Star Wars franchise.
- The layout inside the Sand Worm's sand trap appears be a homage to the vases from Super Mario Bros. 2, which most prominently also appear in the desert level of that game.