One of the more puzzling non-changes in the D&D 2024 edition refresh is that they didn’t make any changes to damage vulnerability.
In 5e D&D (both 2014 and 2024), resistance to a damage type means you take half the damage. This is fine. Conversely, vulnerability to damage means you take double the damage. This is too much damage!
You know how I know vulnerability is overcooked? The designers don’t trust it. They knew it was a problem when they wrote the 2014 Monster Manual. You can tell because vulnerability is so incredibly rare in 5e.
5e is the least vulnerability-happy edition since the mechanic took flight in 3e. The 3e Monster Manual had something like 50 monsters with vulnerabilities; the 4e MM had about 75; and then 5e reduced the trend with about 20. In the 2014 MM, vulnerability exists in a dozen or so CR 1 or lower monsters, like skeletons (bludgeoning vulnerability) and awakened shrubs (fire vulnerability), and then in only 10 monsters of CR 2 or higher: shadow demon, earth elemental, mummy, mummy lord, rakshasa (sort of), salamander, minotaur skeleton, treant, and awakened tree. It’s kind of a weird mechanic in that at low levels it teaches you that you can occasionally target a monster’s weakness, but then it un-trains that mechanic at high levels.
Notable high-level monsters are missing obvious vulnerabilities. You’d think that since salamanders have cold vulnerabilities, so would other fire monsters, like fire elementals, red dragons and fire giants, right? and vice versa, cold monsters would have fire vulnerabilities? White dragons, winter wolves, and frost giants don’t. Hey, earth elementals are vulnerable to thunder: so are stone giants or gargoyles or dao or stone golems? No.
The lack of vulnerabilities is a problem because it goes against player expectations. New and intermediate players (basically anyone who hasn’t memorized the Monster Manual) tend to make strategic decisions like targeting cold attacks against fire creatures. These are intelligent, cool in-game decisions and they should be rewarded, but they aren’t (unless the DM houserules monsters)!
Why are there so few vulnerabilities? Vulnerability is way too powerful! When a monster has a vulnerability, if you have the right damage type available (and, let’s face it, at high levels you probably do), you can trivialize a fight, dealing damage at a 2-for-1 rate. D&D isn’t the type of game, like Pokemon, where the game is tuned around the expectation that you’re frequently hitting vulnerabilities. D&D in fact is not wild about you trivializing fights at all (see Legendary Resistance). Especially at high levels, D&D really wants to avoid anticlimax and high levels of swinginess. You shouldn’t drop that campaign villain in one round. Therefore, no ancient red dragon cold vulnerability!
The problem could be tweaked by adjusting the definition of vulnerability. In 3e (and Pathfinder), vulnerability means you take 50% extra damage from your vulnerability. In 4e (and in Pathfinder 2), creatures have a specific number next to their vulnerability: “fire 10” means you take an extra 10 damage when you take any fire damage. Both of these are less extreme than a flat 2x damage.
The 2024 edition could have rewritten vulnerability by changing just a few sentences in the core books. They could have used some version of the 3e or 4e rules or come up with something new. Instead, they stayed with what they knew doesn’t work – and continued to push vulnerability under the rug. There are more than a hundred new stat blocks in the 2024 MM, but the same number of vulnerabilities.
As monster designers, what are we to do? As the 5e designers know, vulnerability is nigh unusable. What I usually do, in Monstrous Menagerie and other monster books, is add, not a vulnerability, but some other unique interaction with a damage type or other form of damage, similar to WOTC 5e’s Flesh Golem. The flesh golem isn’t vulnerable to fire, but has an Aversion to Fire trait that gives it disadvantage when it takes fire damage. That’s a more interesting mechanic anyway, and I’d be happy to see more like that. If fire doesn’t deal double damage to your fire-weak custom monster, what does it do to them instead? Set an Oil Golem on fire? Send a Wood Golem running amok, or running away? Melt a Snow Golem and temporarily reduce its size? Even if vulnerability is nigh worthless, there are a ton of interesting options beyond vulnerability. But still – I would have liked to see vulnerability rebalanced so it was a useful tool.
