Errata

     To begin, it must be noted that these optional rules in no way effect "true" lycanthropes. Only characters and creatures who have become infected with the disease known as lycanthropy are affected by this rule system.

Basics

     Lycanthropy on Tryll is handled in a slightly different style than on most campaign worlds. On Tryll, there are no moons, therefore the lycanthropic cycle cannot be driven by lunar cycle(s).
     On Tryll, a lycanthrope's cycles are instead determined by his own physical and mental stamina. It is a simple system, derived by determining the lycanthrope's Wisdom and Constitution scores.
     The rationale is this: the higher the lycanthrope's Constitution, the more often he can stand the stresses he undergoes when changing into were-form. Conversely, the higher his Wisdom, the more likely it is that he can resist the subconscious impulses which trigger that change.
     When a character becomes infected with lycanthropy, the DM must determine the percentage chance that character has of changing into his were-form. This is a flat 5% chance, modified by the following formula.
     First, the DM must determine the character's Hit Point Adjustment (as per Constitution). This number is added to the base 5%. This is because the stronger the character's Constitution, the more often he can stand the stresses associated with the lycanthropic change.
     Next, the DM must determine the character's Magical Defense Adjustment (as per Wisdom). This number is subtracted from the base 5%. Character's with higher Wisdom scores are better able to resist the subconscious impulses which trigger the transformation into were-form.
     If the chance is less than 1%, it is automatically increased to 1%. The formula appears below.

     Every day, the DM must roll percentile dice. If the die roll is equal to or less than the character's chance of entering were-form, then the change will be triggered exactly at midnight. Note, the chances are cumulative, so the change is inevitable. Once the character has transformed, the cumulative chance is set back to 0%.
     This means that characters on Tryll infected with lycanthropy are unable to predict exactly when they will change to were-form; at best, they will know only how likely the change is, and that only through observation (a player should not be aware of what the base chance is).
     This also means that the were-form transformation is a random process - it might be three weeks between changes, then three days, then a month.

Different Were-Creatures

     Different types of were-creatures also modify the chance of change. Some were-forms are more powerful than others, and can trigger the changes earlier. Others are weaker, and the changes occur less often. Again, it must be noted that the base chance for transformation cannot fall below 1%.
     The table below details the most common were-forms, and their modifications of the base chance.

Ending the Were-State

     In order to be cured of lycanthropy, the character must undergo the usual method laid out in standard AD&D resources.