FREQUENCY: Uncommon ([Temperate Wilderness Swamp])
FREQUENCY: Uncommon ([Temperate Freshwater Surface])
FREQUENCY: Uncommon ([Temperate Freshwater Depths])

FREQUENCY: Uncommon ([Tropical Wilderness Swamp])
FREQUENCY: Uncommon ([Tropical Freshwater Surface], [Tropical Freshwater Depths])

FREQUENCY: Rare ([Dungeon Level IV])

NO. APPEARING: 4-16
ARMOR CLASS: 9
MOVE: 3"
HIT DICE: 1-4
% IN LAIR: Nil
TREASURE TYPE: Nil
NO. OF ATTACKS: 1 ~ 19 (HD 1) | 1 ~ 16 (HD 2-3) | 1 ~ 15 (HD 4)
DAMAGE/ATTACK: 1-4 <don't roll?>
SPECIAL ATTACKS: Drain blood, anesthesia, disease <order: Anesthesia, drain blood, disease?>
SPECIAL DEFENSES: Nil
INTELLIGENCE: Non-
ALIGNMENT: Neutral
SIZE: S to M <assign to HD><1=S, 2-3=M, 4=L>
LEVEL/X.P. VALUE: IV | 160 + 4 <XP for a Giant Leech>

Giant leeches range from 1 to 4 HD in size; various sized creatures usually are found in the same group.

They can be killed by attack or with quantities of salt sprinkled on their bodies. <damage from salt cantrip = ?> <as acid, or, holy water>

Found only in the fetid waters of swamps and marshes,

ENCOUNTER: giant leeches are a threat to any warm-blooded creature which passes within their movement range of 3".
Giant leeches will come out of water at night to attack prey within 3". <moved>
These horrors wait in the mud && slime far prey, and as it passes they strike.

Drain Blood: The initial attack also attaches the sucker mouth of the giant leech,
and on the next melee round,
and on each round thereofter,
it will drain blood the equivalent of 1 hit point damage per hit die it possesses.
    Anesthesia: There is only a 1% chance that the victim will be aware of the attack unless it comes out of the water, for the leech has anesthetizing saliva,
        and its bite and blood drain are not usually felt until weakness (loss of 50% of hit points) makes the victim aware that something is amiss.
    Disease: There is a 50% chance that the bite of one of these creatures will cause disease which will be fatal in 2-5 weeks unless cured.

Those that are not truly proprietary are:

rot grub--based on a common insect, but not very popular
giant leech--similar to an LA game blindworm
thoul--a critter never detailed in and form of the D&D game and which I have included in the monsters found in the CZ dungeons already
lungs are already covered as dragons in the LA game, with

I guess I'll work up the thoul for the LA game critters then 

Cheers,
Gary