The way I like to describe it is that 4e and Pre-4e D&D had a baby, and then the baby grew up and went off to school where it started hanging out with these weird indie games and when it came home it was talking about all this stuff like failing forward and shared narrative control.
If I had to bullet point it:
- 13th Age basically feels quite a bit like D&D. If you like D&D, there's a pretty good chance that you'll like 13th Age. If you don't like D&D, you might still like 13th Age (depending on what bugs you about D&D), but it might be more of a stretch.
- 13th Age is more lightweight than any recent edition of D&D, though probably can't be called truly lightweight.
- 13th Age compresses everything down to ten levels, but each level is really dense.
- 13th Age is big on stories and hooks, and is less worried about mechanical fiddliness than most editions of D&D. If you like lots of +2 and -2 for this and that it wouldn't be hard to patch it in, but 13th Age's default position is to not sweat the modifiers too much.
- 13th Age is big on improvisation and shared narrative control. For example, most non-combat spell effects are created by converting a related spell, subject only to your imagination and DM approval. Want to make a fireworks show? There's no fireworks spell, but you can convert your prepared Fireball spell into one. Rogues can even spend a talent on an ability that says little more than "when you improvise some cool combat maneuver, you're way more likely to succeed." Rangers can take an ability that lets them reliably pull off improvised terrain-related stunts.
- 13th Age isn't "4e Pathfinder". While it does show some 4e influence (attacker rolls, for example), it's wildly different in many truly enormous ways. If you're looking for a revised and cleaned-up version of 4e you might still like 13th Age, but it isn't that.
- 13th Age isn't as riddled with opportunities to put together various mechanical options pulled together from different places to put together something crazy powerful/cool as some D&D editions are. For some players, this is a plus, since you don't have to worry as much about system mastery; for players (like me) who enjoy trying to rig together cool combinations, it's kind of lacking in that department.
- 13th Age is fast. It's faster than 4e or 3.5, and without being rocket-taggy. (Well, it's initially not super fast, until everyone gets into thinking about space the way 13th Age does.)
- 13th Age's default setting is a land mass surrounding a mostly-tamed inland sea that empties into a very much untamed ocean. There are thirteen powerful figures called "Icons" that inhabit this region, with various goals and priorities. They're intentionally a little loosely defined, but are a variety of fantasy archetypes - the archmage, the emperor, the high druid, the lich king, etc. In addition to being very powerful individuals, they're sort of stand-ins for the general forces and organizations that'd be associated with them. For example, the priestess is a single individual, but sort of stands for the beneficent deities and the church in general. The Orc Lord stands for the marauding forces of brutal and aggressive monster races in general. This will make more sense in a minute.
- One of 13th Age's unique mechanics is that PCs have a few "relationship points" with various icons. These can be positive, negative, or conflicted. These don't necessarily mean that you have a personal relationship with one of the icons (given their stature, it's not even necessarily likely), but can represent some kind of ties to the general forces they represent. For example, if you were raised in a hellhole you might have a conflicted relationship with the diabolist, even if you've never met the diabolist personally and she's never even heard of you.
- Your relationships come into play in a variety of ways. First, they're a way of hooking characters into the world. Second, at the beginning of each day/session/whatever, you roll a d6 for each relationship point you have. Each six means that your relationship will benefit you in some way that day - the DM will often decide how, but you can suggest that that's what's happening yourself if a situation comes up where it seems appropriate. Each five means that your relationship will benefit you that day - but will also bring a complication along with it! Note that even negative relationships still benefit you; the benefit just arises from your adversity. For example, if you have a negative relationship with the orc lord and roll a six, a common enemy of the orc lord might provide aid to you, or your special knowledge of the cultural traditions of the orcs might confer you a major benefit. If you roll a five, maybe some orcish outriders attack you as soon as they smell you inside your tent instead of riding past (the complication), but beating them up allows you to intercept an important message that they were supposed to be delivering (the benefit.)
- 13th Age characters have something called their "One Unique Thing", which is something nonmechanical that's special about them. (It can be literally unique or it can just be kind of special, and it can be something that totally shapes the character's life, or it can just kind of be a quirk.) This is just there to provide extra hooks into the character.
- 13th Age magic items (real ones, not things like potions) have personalities. They're not generally intelligent in the normal sense of an intelligent magic item, but they exert a slight influence over the people who use them. Normally it's possible to suppress this influence, but if a character tries to command too many magic items, they start to overwhelm him or her. Magic items, by default, are pretty rare and can't be reliably or efficiently produced (again, except for potion-level things, which are generally purchasable), but a character sometimes has to choose which magic items they want to actually use.
- 13th Age doesn't have skills or NWP or anything. Instead it has backgrounds, which are just things you make up. So "raised in a hellhole" might be a background, or "machinist" might be a background or "sewer explorer" or "mariner" or "arcane historian" or basically anything that's part of your character's past. Then, when you make an an ability check, if your background is relevant, you add its bonus to the check.
- MANABARBS! That's broken! Isn't "Librarian athlete diplomat" a better background than "egg checker"? Yeah, it is. It's up to the DM (that's why the DM is a person) to adjudicate what's a reasonable scope for a background, and also when a background applies. Players are also encouraged to riff on their backgrounds to expand their character's identity. The result is that backgrounds that are actually backgrounds instead of just a skill are often more interesting; someone with an "Arcane Lore" background has less to work with creatively than someone with an "Assistant Professor of Arcane Studies at the Santa Cora campus of the Archmage's University." This is kind of a transition for people more familiar with D&D; the idea that you can just write "Street-level scumbag +3" on your sheet and be good at exactly the things you'd imagine the character is good at is kind of an adjustment.
- Also, every class gets the same large-ish number of background points. A few classes can get more, but they're spending class-specific options to do so.
- Classes vary in complexity, but not (too greatly) in power, although different classes are obviously good at different things.
- Every class gets some talents, which are big class features chosen from a list. For example, Paladins have three talents at level one. (And eventually have five; paladins are one of a few simple classes that are built primarily using talents, rather than a combination of talents and spells and stuff.) They can spend a talent on lay on hands, on the ability to have something vaguely like a 4e Mark, on letting them make saves better, on limited spellcasting, and so on. All paladins can smite, but which other paladin-y features you want is up to you. Most class's talents are kind of a hodgepodge of different things you could be good at, but for Clerics, their talents are their domains, and for sorcerers, their talents are related to the source of their power (raw arcanistry, dragon blood, infernal influence, etc.), although that can be refluffed.
- Some classes have spells (Sorcerers, Wizards, Clerics and Bards by default; Paladins and Rangers with talents). Spells are basically like 3.5 spells, with the following exceptions: First, as you level up, you only get a few more spell slots but your spell slots are gradually shifted to higher levels. For example, at level 1 you have five level 1 spell slots. At level 8, you have three level 5 spell slots and eight level 7 spell slots, and that's it. (There are no even-level spell levels, and spell levels are the same as the level you gain access to them.) The fact that you lose lower-level spell slots is okay, though, because you can and should continue to prepare lower-level spells in higher-level slots. Ray of Frost, for example, does 3d6 damage when prepared as a level 1 spell. If you prepare it in a level 7 spell slot, it does 7d10 damage! This allows you to use your favorite spells throughout your career if you wish, and also makes it so that the number of choices you have increases as you level, since it's perfectly valid to prepare a level one spell in a level 7 slot, since that increases its power to the power of a level 7 spell.
- Additionally, whether a spell is at-will, per-encounter, daily, or some other recharge mechanism depends on the spell itself. So you could prepare one at-will spell, or three, or none. The next day you could change it around.
- Rogues know a certain number of at-will maneuvers, sort of like 4e, if all their abilities were at-will. (Although some can only be used in certain circumstances, there's no limit (mostly) on use per battle or per day.)
- Fighters and bards know a certain number of flexible attacks. These are basically like crits, except they're trigger on various types of rolls instead of on just a 20. For example, a fighter who knows how to Shield Bash who rolls an even roll on an attack while he or she is using a shield can shove the enemy away so they're no longer engaged. (13th Age doesn't worry about exact positioning, but does worry about whether you're specifically engaged with somebody.)
- Bards also knows songs. Songs are like spells with some extra rules. Bards are not one of the simple classes.
- Classes also have feats, but feats are not chosen from a huge list of general feats available to anybody (although there are a small number of general feats that do things like give extra background points ). Rather, feats are chosen to improve specific talents, spells and maneuvers you know, and they're listed right with that option. For example, consider Ray of Frost. By default, Ray of Frost does some cold damage, as it does in 3.5. If you use a feat to improve it, you give it the potential to daze enemies you hit with it. If you use a second feat, its range increases. If you use a third feat, you can change its damage type. Rather than wading through a huge pile of general feats, you know which feats are options for you because they're listed right with the character options that you're using.
- Race is very lightweight in 13th Age. You get stat bumps, maybe an activated or triggered ability, and maybe one other ability. If you think that being an elf should give you a bunch of bonuses to various checks and stuff, you can spend background points emphasizing your elfiness.
- Additionally, both race and class give you a stat bump in 13th Age (your choice from one of two options). However, you can't chose the same stat for both. This completely eliminates the D&D phenomenon where races with a stat bump to a class's main action stat were just the best at that class. Instead of there just being an ordered list of races for each class, where this race is the best, then this race, then these races, and these are the worst, there's much more of a sense that different races are just bringing different things to the table. (Exception: Half-Orcs, which annoyingly have a narrow racial ability that only applies to melee attacks. We should know better than that by now.)
- In the interest of fairness, there are two issues that I consider slight drawbacks of 13th Age, at least as it exists now:
- First, 13th Age's core is one 320 page book. That's a long book, but it's the same length as the 3.5 or 4e PHB, while trying to serve as a PHB, DMG, setting book, sample adventure (it comes with a sample adventure), and monster manual. If you add that up, it's pretty clear that something has to give. The things that appear to have "given" are character option density and art density. There are cases, especially at low levels, where you're choosing more character options than you aren't. Sorcerers, for example, prepare 4 spells at level 1. Sorcerers have six level 1 spells. So you end up prepping most of them. That rapidly alleviates itself at higher levels (remember that level 1 spells stay reasonable choices forever, so by later levels you have tons of choices), but there are places where the pagecount pinch is definitely felt. Additionally, the Druid and Monk didn't make the PHB. They're joining the Chaos Shaman, Battle Captain, Occultist, and Necromancer in the first expansion book. However, they'll be available to people who pre-ordered the core book as well. (They felt that since they at once point announced the monk as part of the core book, it was fair to still offer the class to people who ordered the core book, even though it's actually appearing in 13 True Ways, the expansion book.) Another part of the pagecount pinch is that some types of abilities, such as in-combat summoning, aren't represented in the book directly. (A spellcaster could still summon a creature outside of combat with a ritual and try to coerce it or persuade it to lend a hand, but summoning mindlessly loyal minion creatures isn't represented.) Finally, while 13th Age's art is beautiful and I think would have broad appeal (it contains full-color portraits of each icon, as well as some lovely understated pencil-art style art), there's only so much of it. The place where this is most obvious is in the monster section, where each monster gets a neat runic token representing it, but not a full portrait.
- The second criticism I can think of of the system is that the rules for spell preparation, retraining, and spells known could probably use an FAQ. It's possible to piece together a coherent and consistent set of rules for it, but it requires pulling in bits and pieces of rules from all over the place. (For example, the game isn't generally clear about whether you can prepare a spell more than once for a given day -- except that there's a wizard talent that lets you do that, meaning that the not-stated default rule is that you can't. But if you're making a bard character, it probably doesn't occur to you to look for rules for your class buried in the wizard class options. That's the most egregious example, but there's a bunch of other non-obviousness.) Knowledge of how 3.5 spellcasting works is both a blessing and a curse, since assuming that things work the same as 3.5 is sometimes correct, but often not correct. The 13th Age rules are for the most part generally well-written, and loaded with sidebars suggesting ways that you can screw with them to various effect. (It's definitely not a system that cares if you mess around with it.) It's just that for some reason there's not a complete section where all of the spellcasting rules are listed in one place, and I feel like literally everybody who picks up the system goes through the same dance of trying to figure out how spell preparation is supposed to work.
So that wasn't really that short. Oh well. Either way, I'd really, really recommend 13th Age. It's an incredible system overall.
