Real world bomnardier beetles produce hydroquinone and hydrogen peroxide in two different sacs. The to do sort of react, but slowly, until you add a catalyst. If you're doing this for fun you can use various metal salts to make it fizz, but of course thats not how things work in biology. The beetle also produces a peroxidase enzyme, that gets the reaction going, and its quite spectacular. Obviously this is something you've got to use as a D&D creature!
I've chosen to make them essentially harmless creatures not interested in a fight, but very capable of defending themselves. It seems to fit.
Note that really clever players might try and use this chemical (alchemical) process for their own advantage. I've left it open to interpretation how well that should work.
Bombardier Beetle, Giant
by Cab Davidson
| Stat | Bombardier Beetle |
| AC: | 3 |
| HD: | 7* |
| Movement: | 90' (30') |
| Attacks: | 1 spray |
| Damage: | 9d6 |
| No. Appearing: | 1 (2d4) |
| Save As: | F4 |
| Morale: | 5 |
| Treasure Type: | Nil(special) |
| Intelligence: | 0 |
| Alignment: | Neutral |
| XP Value: | 850 |
The giant bombardier beetle is an 8’ long, 5’ high, robust bodied beetle with yellow stripes running down the length of its otherwise brown carapace. Its bulky abdomen is offset by its narrow abdomen and comically small head and mouthparts. The bombardier looks harmless, and if left alone it is. It wants nothing more than to eat its way through the rotting material on a forest floor, perhaps wandering in to caves to graze on any fungi therein. At first glance, other than it thick carapace, it would appear defenceless. That appearance is deceptive.
If threatened a bombardier beetle will spray any foe within 10’ with a complex alchemical mixture. While this mixture originates at the tip of its abdomen it can point it in any direction, including upwards, downwards, and straight in front of it. A normal hit roll is required, and if it hits then the mixture of fluids reacts to create boiling heat, inflicting 9d6 damage to the target. It can do so 6 times before needing to recharge, one charge being regained per hour.
They are otherwise completely non-aggressive. They will not pursue a fleeing foe, they will not continue an attack beyond a point when an attacker is no longer attacking them, and will return to their normal grazing as soon as danger has passed.
While they do not hunt or hoard, so they have no treasure as such, alchemists may cover the alchemical ingredients that the bombardiers use to create their spectacular attack. To extract these three ingredients is, however, complex and fraught with danger, and it is unlikely that multiple piercing or stabbing wounds inflicted to a bombardier beetle will leave them intact. But each of the three organs that make and store these components may have a value of 100gp per charge remaining when the beetle died, to the right alchemist.