My D100 System

This coming friday, our regular Dungeon Master, AJ (who runs a great game and stepped up when I had to take a break) will be out of town. I volunteered to run a short adventure. I haven't run anything since April, so I'm hoping it goes well (even after almost 30 years as a DM, I still get butterflies).

At the moment, I'm trying to decide if I want to us the D100 rules I've been working on.

First you need a character sheet, Basic Role Play or Call of Cthulhu will work.

The way the rules work is that the Game Master sets the difficulty of a task, generally 30%, 50%, or 70% which is then modified by the Character's bonus, if any, in the appropriate Skill.  

Let's say I have the Spot Hidden skill at +10% and I'm looking around a darkened room. The difficulty is 20% which is added to my Spot Hidden skill of +10% for a total of 30%.  

Another example is that I'm trying to punch a cultist, the difficulty is 50% and my Brawl skill of +20% is added together for a total of 70%.  Doubles are critical failures or successes. I'm anxious to try this out because I like Percentile systems but am often unhappy with the default values of certain Skills.

Character creation would involve choosing 5 Skills with a +10% bonus, 4 Skills with a +15% bonus, 3 Skills with a +20% bonus, 2 Skills with a +25% bonus, and 1 Skill with a +30% Bonus (this was inspired by an option in the excellent Mythras Companion).

At the moment, I'm not using Characteristics so Hit Points would be equal to 12 + 1d6. While Sanity is equal to 40 + 4d10.

I'm really anxious to try this out.

Any thoughts would be appreciated.