The so-called Beast is just a goofy-looking critter with a single tooth that is no longer than a short sword. It is intelligent, and not particularly malevolent. It is, instead, good at sneaking around settled areas looking for livestock to feed on.
If it succeeds in an attack roll by more than 4 points, the Beast can make an opposed Strength check (vs. +2) to swallow a creature no larger than a halfling whole. Swallowed creatures have a -2d penalty to any rolls, and can only use small weapons already to hand or spells. Swallowed creatures take 1d6 damage each round. If the Beast is damaged while a creature is swallowed, the swallowed creature normally takes half damage.
Rex the Strangler: Init +1; Atk by weapon +4 melee (by weapon+2) or grasp +4 melee (choke); AC 11; HD 3d12+6; hp 25; MV 30’; Act 1d20; SP choke; SV Fort +4, Ref +2, Will +2; AL L.Rex the Strangler will certainly use weapons, but his grasp attack is feared throughout the land. When Rex succeeds with a grasp attack, he grips his opponent's windpipe and begins to choke it to death. Each round of choking (including the first) requires a Fort save. When the first Fort save fails, the opponent is unconscious. When the third Fort save fails, the opponent dies. The initial DC is 10, but the save DC increases by +4 for every additional round Rex the Strangler maintains his grip.