The skill check is a simple part of the entire d20 family of gaming systems, and it’s about as simple as it gets. Need to find a letter in a box? Roll a d20 and add the appropriate skill modifier. Need to forge a weapon? Roll a d20. Need to convince a visiting noble to back you at the gala? Roll a d20. Need to disarm a complex trap in the middle of combat or navigate through a forest? roll a d20.
It gets dull when everything other than combat is just resolved by rolling a d20. There’s a single moment of tension and then no matter how complex the task it’s over instantly.
Which is why I like to play around and do something different once in a while.
Cumulative Skill check
A ranger is working their way across the countryside over several days, trying not to get lost in the wilderness.
The wizard is painstakingly deciphering a magical tome.
A blacksmith is slowly assembling the parts of a large and complex weapon.
All of these cases involve a single character making incremental process towards a goal that is almost certain to be reached eventually, assuming the character is reasonably skilled. Rather than representing this with a single skill check, where success or failure is determined all at once, they can instead be represented by a series of cumulative skill checks.
A cumulative skill check is made primarily by one character over a long period of time. Each day, the primary character makes a skill check to represent the progress they have made that day, adding their skill modifier as usual. Then, however, the GM subtracts from that total a modifier based on the difficulty – typically beginning at 10 for simple tasks, and ranging as high as 20 for complex ones. The result is then added to the check’s running total. When that total reaches a particular goal, the party is successful.
Using this system, your party will have good days and bad days – but will rarely suffer a catastrophic failure. You don’t have to worry about wasting huge values of materials in a poor spellcraft roll, or simply failing to navigate the wilderness. It allows players to consider setbacks and gives them a level of adventure beyond the instant success and failure of a single die roll.