Sarah Darkmagic, presumably of the New Hampshire Darkmagics, has an interesting self-review of a very cool encounter she’s creating for a delve. In this article, she’s trying to figure out how the PCs would wrest control of a bunch of hostile flying sawblades controlled by a gnomish psion of some sort. Her thoughts are that it would require a check using Arcana, Religion, or Psionics. The trouble is, there is no Psionics skill. She effectively hand-waves this by simply saying that anyone who is a member of a psionic class has this skill. At first, I had the knee-jerk reaction of, “Hey, you can’t do that! That’s not in The Rules!” But then I actually sat back and thought about it for a second. Here’s what I came up with.
It’s fairly well known that the D&D skill list, while it covers most things you’d want to do in most encounters, doesn’t cover everything. There are a number of mundane skills not covered, as well as a number of very nitch or situational skills that are absent. This is fine most of the time; most of the time you will not need these skills, so it doesn’t make sense for your players to have to spend their precious skill training on skills that are unlikely to be used more than once or twice.
But what happens when you do need those skills? What happens when the PCs are trying to land a rapidly descending airship after the pilot has been thrown overboard? What happens when the PCs run out of arrows in the wilderness, and they must make their own? There is no Pilot skill, nor is there a Fletcher skill, so what do you do? You could just hand-wave these things, or you could try to shoe-horn a somewhat related skill into that role. Perhaps Athletics is used to turn the wheel of the ship, or Nature is used to find the right kind of wood and form it into the shaft of an arrow. But neither of these solutions is completely satisfying.
That’s where aptitudes come in. Aptitudes function much like skills: you are either trained or untrained in an aptitude (gaining the +5 bonus or not), you get a bonus from a relevant ability score, and you get a bonus equal to half your level. They are used the same way, as well: when an aptitude check is called for, you roll a d20, add your aptitude bonus, and compare the result to a DC. Aptitudes can be used in combat encounters, and they can be used in skill challenges.
There are a few differences, however, between aptitudes and skills. First, there is not a limited number of aptitudes. Aptitudes are very specific, and may apply only to a single encounter during an entire campaign. There is not a set list of aptitudes as there is with skills; the DM (or players) create an aptitude when the situation warrants it. Most importantly, you do not spend skill training slots to train in aptitudes. Instead, you are considered to be trained in an aptitude when it makes sense for you to be so.
Let’s look at our two examples above, the crashing airship and the arrows in the wilderness. The players ask you, “What skill should I roll to try to pilot this ship?” You think for a moment and say, “Roll a Pilot check.” They look back at you, confused. That’s not on their character sheets. How do they know whether or not they’re trained? Take a look at your players. The artificer is well versed in creating all manner of magical things, and may have knowledge of airships and how to use them. He doesn’t have anything on his character sheet or in his backstory that contradicts this, so you ask him if he’d like to be trained in Pilot. He says, vehemently, “Yes”, and you ask him to explain why he’s trained. Maybe the two of you do a little flashback sequence to explain it. Now he can contribute to the skill challenge to land the ship in a meaningful way, and you’ve created a little bit of background for him together. The wizard, on the other hand, established in his backstory that she grew up as a hand on an airship, and even apprenticed to the captain for a time. It would make perfect sense for her to be trained in Pilot, so you simply tell her that she is. You tell them that Pilot is Wisdom-based, and ask them to calculate their bonuses.
While tromping through the woods, the party needs to make more arrows. It would make sense for a Nature or Perception check to allow players to find the base materials: good, supple but strong wood, stone or metal for the arrowheads, feathers for the fletching. But to assemble the arrows, neither skill makes perfect sense. Instead, you call for a Fletcher skill. The ranger in the party is an archer, so it would make quite a bit of sense for her to be trained in Fletcher. The fighter, on the other hand, knows a lot about weapons, carries a bow as a backup weapon, and spends a good deal of time whittling during short rests. You ask him if it would make sense for his character to know how to make arrows, and he says, “Sure. My character is a master with wood-carving.” He’s trained, too. You tell them that Fletcher is Dexterity-based, and let them make rolls.
The beauty of this system is that it allows you to call for non-standard, very specific skill checks, does not require your players to spend mechanical effort on being trained in these very specific skills, and it can even generate some background or flavor on the fly.