In this video we're going to look at ability checks, the core interface between characters and the world in D&D. In particular, we're going to look at some details and advanced uses of ability checks to make our games more interesting and more fun.

• The core mechanic: the DM describes the situation, the player describes their intended action, the DM adjudicates the results.
• This is the core interaction in D&D, describe on page 6 of the Player's Handbook. We can often think of our adventures as a whole bunch of these interactions networked together. Each node in this network contains the DM describing the situation, a player describing a intended action, and the DM describing the results.
• One key to this interaction is that we don't know what the rest of the network will look like because we don't know the outcome of any given node. The network forms during the game, not before it.
• Not every core interaction requires a difficulty check (DC), many times the action can just be done. There's no risk and no real chance for failure, so it just happens.
• If there is a chance for failure, the DM determines the difficulty class (DC) of the difficulty and the appropriate ability and potentially relevant skills to use to make that check. The player then rolls on that ability and adds their proficiency if they happen to be trained in a relevant skill.
• We can make our DM's lives easy by choosing a difficulty for a situation on a scale of 1 to 10 and then add 10. That's our DC. How hard is it to open a lock, kick down a door, leap onto a hanging chandelier, or pilot a huge war mech? Ask yourself how hard that is on a scale of 1 to 10 and that's the DC. If it's under DC 10, we don't bother to roll. We can assume the character can succeed without difficulty. If it's above 20, it's likely too hard to accomplish but that may not be the case for highly skilled characters so in some circumstances we can turn the dial up, or past, 11 on some difficulties (DC 21 or higher).
• Improvising DCs is a fantastic improv technique for the lazy DM. Get used to choosing difficulties for improvised actions by the characters.

Failing Forward and Succeeding at a Cost in Complicated Situations?

• Two hugely valuable skills for a DM to build are understanding how to improvise situations so that a single successful or failed skill check won't cause total failure or total success given a situation.
• The 4th edition of D&D had a system called Skill Challenges that built a framework around complicated sets of skills. For many of us these proved too abstract from the situation and too formulaic in their approach. They didn't give players the freedom to choose their own approaches.
• Instead of building abstract mechanical frameworks for complicated skills, spend your time understanding how the situation works in the world. Are cultists performing a complicated ritual to summon a demon? Understand how the ritual works and how it might be disrupted. Make the ritual robust enough that a single check won't completely end it.
• Sometimes you might determine that something is sure to succeed but there may be a cost. Instead of assigning a DC, you can just ask for a roll, see what the result is, and improvise the result based on how good or bad the roll was. If it was really good, things go smoothly. If it was ok, things go ok. If it was bad, they still succeed but with a complication. Maybe someone overheard the commotion or the king is convinced but still not happy about it.
• Sometimes you don't need a DC. Instead you ask for the roll and result and build off of that analog result.
• You don't want the story of an adventure to fall apart because of a single bad check. Be prepared to let the players succeed at a cost or fail forward into the story.

Ability Checks as Improvisation

• The simple mechanic of the ability check is the primary interface between the characters and the world.
• It's also one of the best tools a DM can use to help improvise during the game. The creative descriptions and decisions of the players around the table mixed with the random results of the simple d20 are often what makes our games so unique and interesting. Practice your ability check improv.