One of the first things you'll notice about
Swords & Wizardry Light (SWL), after its small size, is that it only uses two sizes of dice - d20s and d6s. Newer players often have trouble differentiating between the different sized polyhedral, and using just two sizes of dice simplifies things greatly.
One result of this is that monsters, which have a d8 for Hit Dice (HD) is
Swords & Wizardry Complete (SWC), now use a d6 for HD in
SWL.
That changes the power curve, right?
Not really. If you figure the Long Sword is the base weapon for damage in
SWC, it does d8 damage, same as the HD size of a
SWC monster. In
SWL, that Long Sword does 1d6 damage, same as the HD size of a
SWL monster.
Where the power curve does change a bit is with casters. That Magic Missile spell which did either 1d6+1 with a hit roll needed (basically the same avg as a 1d8) OR 1d4+1 with no roll needed to hit (basically the same avg as a 1d6) in
SWC is now, in
SWL, 1d6 no roll to hit needed. In many ways, its the best of both options from
SWC - no hit roll needed AND a full HD die of damage.
When we consider optional rules that will allow higher level casters, spells like Fireball and Lightning Bolt will become more powerful if not tweaked - area effect damage spells that potentially effect a full HD per die, not 3/4s of a full HD as it is in
SWC. Something to think about as we move forward.
So, how does one convert monsters from
Swords & Wizardry Complete or other OSR sources to Swords & Wizardry Light?
If you are converting a monster from a monster section, monster bestiary or such, remember to roll the Hit Points (HP) using d6s. Monster damage will be rolled using d6s also. So, 1d4 becomes 1d6-1 and 1d8 becomes 1d6+1. For larger damage numbers, add the low end of the damage indicated to the high end. Divide by 3.5 - this is the approximate number of d6s it converts to.
To adjust the Hit Points (HP) of the monster in question for an adventure, for each HD of the creature (assuming a d8 for the HD size in the source material) subtract one HP from the total of the creature. If the total is still higher than HDx6, either lower the total to HDx6 or subtract one HP per HD again. Obviously, the first option give you a much stronger adversary.