Considering how frequently I write about it on this blog (with the exception of the past couple of months; blame a creative dry spell), it should come as no surprise that 13th Age is one of my favorite RPGs right now. My first long-term campaign went up to 5th level (barely), but it stretched each level out over a long period of time. An Incremental Advance every 2-3 sessions. For our current campaign (which features rotating GMs), we've been awarding an Incremental Advance every session, and after the 3rd one we gain a level. We've just now reached the same point at which I ended the last campaign - level 5 - but one of the explicit goals has been to experience high level play.
I already dislike it. Granted I've never preferred high level play in D&D, but 13th Age is especially egregious with its number inflation. Unfortunately, it's sort of a double-edged sword because the numbers scale the way that they do precisely to maintain an even progression over the course of a PC's adventuring career. In other words, damage scales at about the same rate as HP. Since you gain a weapon die for damage every level, HP has to become pretty inflated to keep up. While I haven't crunched the numbers in detail, my experience seems to be that PCs will drop after suffering around the same number of hits from an appropriately challenging foe regardless of level. In most editions of D&D it seemed like low-level characters were quite fragile, but at higher levels they could soak up more attacks due to their increasingly-inflating HP (to the point that high-level combat skewed even further toward "rocket tag" of save or die/suck abilities to bypass HP entirely). This smooth-scaling in 13th Age is desirable to me, but I really wish it could be more tightly bounded (like, and I can't believe I'm saying this, D&D 5E).
So why is this even a big deal? Well, mostly because when you start dealing with bigger numbers, the math gets just a tad slower. I've noticed that my PC's turns go a little slower than at low levels (though at least one player doesn't think it's a big deal), but the real annoyance has been GMing. I've got at least as many monsters to run as there are PCs in the party (and usually more), and I like to get through NPC turns quickly to maintain momentum. I feel like those few extra seconds per NPC (per turn) starts to add up, and I occasionally find that it distracts me from interesting tactical and narrative embellishments in combat.
A Possible Solution
Obviously I'm not going to stop playing 13th Age because of this. And as much as I prefer the alternative of "bounded accuracy" espoused by D&D 5E, from what I've seen of 5E so far 13th Age simply hits way more of my other preferences in an RPG. Besides that, my group has been instictively negative toward 5E despite knowing little to nothing about it.
Thus, I'd like to try to make high-level play in 13th Age more manageable. Based on the numbers that were being thrown around in last night's session (again, this is at level 5), I'm considering simply rounding monster HP and player damage to the nearest 5. None of this "always round down in D&D" legacy crap, either. Standard rounding rules simply make more sense because theoretically you should be rounding up about as often as you round down, and so your rounding would effectively "cancel" each other out. Obviously results will skew slightly up or down in any given combat, but is this really any different from earlier editions of D&D where monsters got variable HP by rolling Hit Dice?
Barbarian: "I crit for 94 damage" (because that literally happened last night, on the first attack, vs a 200 HP dragon)
GM: mentally rounds that up to 95 and notes that the dragon has 105 HP left
Wizard: "I deal 32 damage with Ray of Frost."
GM: Rounds that down to 30, so the dragon's at 75 now.
Multiples of 5 are easy, because we deal with them every single day. I have to think for a couple of seconds longer when I subtract 94 from 200, and if I'm starting from a value that's not an easy multiple it takes longer still. Like, say, subtracting 32 from that dragon that now has 106 HP if tracked by RAW. In my head I would generally do this in 2 steps by first subtracting 30 from 106, and then subtracting 2 from 76. Which is tougher if I'm dealing with odd numbers, and tougher still when one or more players is talking (especially if they're correcting their damage, whether that's from math errors or forgotten bonuses. Sometimes I have to start the mental math over from scratch when that happens).
Some people might be faster at mental math than me, and others still might not be but don't mind the cumulative time lost. For me though? Rounding seems like a really promising solution, because those huge numbers are just an unnecessary amount of granularity.
The Gumshoe Precedent
After coming up with this solution, I was reminded of a rule from the Gumshoe game "Night's Black Agents." To quote from page 215 which is a summary of Hit Threshold Modifiers: "In games using the full range of options and tactical rules, Hit Thresholds can vary widely. Try to rebalance those values if you can: if one combatant has a Hit Threshold of 7 and one has a Hit Threshold of 9, run their combat as if they had Hit Thresholds of 3 and 5, respectively. This keeps fights shorter and more dangerous, and therefore more exciting."
This is particularly useful to keep in mind in Night's Black Agents because the die that you use to resolve actions is a d6. The principle isn't as mechanically necessary in 13th Age, but it sure helps to simplify that math. You're effectively treating each increment of 5 as a value of 1, turning a 100 HP creature into one with effectively 20 HP. That 30 damage attack becomes 6 damage. 14 out of 20 is the exact same ratio as 70 out of 100.
Once you get into Epic tier and the numbers get higher still, it will become practical to mentally round to the nearest 10. I'm not quite sure where the best cut off points will be (I haven't playtested this yet), but I'm thinking it will probably feel pretty intuitive once you start dealing with numbers of a certain size.
Also worth noting is that you don't have to necessarily institute a sweeping house rule for this. You don't even have to tell your players you're doing it. Just do the conversion to simplify the math, and they may never be the wiser. It's the best of both worlds, actually: your players get to feel uber powerful by throwing around high damage attacks, but by rounding the values you don't have to deal with the mathematical challenges of quickly adding and subtracting high value numbers to the nearest one.