FREQUENCY: Rare
FREQUENCY: Rare ([Dungeon Level IV])
FREQUENCY: Very rare ([Temperate Freshwater Depths])
FREQUENCY: Very rare ([Tropical Freshwater Depths])
NO. APPEARING: 1-4
ARMOR CLASS: 4
MOVE: 6"
HIT DICE: 6
% IN LAIR: 50%
TREASURE TYPE: [Q]
NO. OF ATTACKS: 1
DAMAGE/ATTACK: 1-8 + blood drain
SPECIAL ATTACKS: Nil
SPECIAL DEFENSES: Nil
MAGIC RESISTANCE: Standard
INTELLIGENCE: Non-
ALIGNMENT: Neutral
SIZE: L (20' long)
LEVEL/X.P. VALUE: IV | 225 + 6

Giant bloodworms are usu. found in the shallow pools of
underground caverns. They cannot swim, but propel themselves along
the bottom of such pools or on nearby firm ground. Their underbelly
is a dark slimy brown while their upper surface is a mottled green.
Lying half in, half out of a pool, a giant bloodworm is easily mistaken
in dim light for a moss-covered boulder.

A giant bloodworm will only attack if hungry (they will eat once a week) or
if trodden on. When the giant bloodworm does attack, it will
attempt to fasten its large suckered mouth onto a victim. If successful,
it will drain blood from its victim each subsequent round. Though
the initial attack requires a successful 'to hit' roll and causes no damage,
subsequent blood drains are automatic, requiring no 'to hit'
roll, and deliver 1-8 points of damage until the bloodworm dies
or releases its grasp.

Giant bloodworms are particularly vulnerable to fire -- they take <x2> damage
from all fire attacks and save at -2 against magical fire. A successful fire attack is
the only way, short of killing the beast,
to force it to relax its grip on a victim, though if the bloodworm is
not killed, it will attempt to re-attach itself to a victim immediately.
 

        by Ian Livingstone

UA:
The giant bloodworm surprises the party if they are not moving in SEARCH mode. (theory)