BX Monsters A to Z: Crab, Giant

 And now, the scourge of the sea floor, the beast of the beach, the ravenous reaver of the riverbed... the giant crab!

By the book, this thing is a heavy-duty killing machine. The description is one of the briefest in all of B/X D&D, at a mere three sentences. These tell us that giant crabs can't swim and are found on beaches, in coastal shallows and rivers, and in salt or fresh water, that they are always hungry and attack anything that moves, and that they are not intelligent. That last bit seems rather an odd thing to mention, considering  most D&D players and DMs surely already know that crabs aren't intelligent, and how many much more ambiguous cases of monster intelligence go entirely unremarked in their descriptions. Oh well. I guess maybe the authors were determined not to leave the description at only two sentences, and that was the best they could come up with. What is interesting here is that the giant crab is one of the very rare creatures that will always attack; no reaction roll needed. 

If you're a Basic or low-Expert level adventurer, you do not want to mess with these things. They're virtual tanks, with an AC of 2, equal to plate and shield. At 3 HD, they're as tough as a wild boar or a warhorse, and presumably in the same neighborhood of size and bulk, or perhaps a bit smaller. Invertebrates tend to be a bit more resilient, pound for pound, after all. Or perhaps not. The damage these critters do is nothing short of ridiculous: two claw attacks for a whopping 2-12 points each. That's more total damage potential than any kind of bear except the cave bear. That's equal to a tiger or a freaking white dragon, both notoriously fearsome creatures with twice the giant crab's Hit Dice and very sharp claws and teeth. A crab's claws are not razor-sharp; they're adapted much more for gripping than for shearing or tearing, and there's nothing in the description to suggest the giant crab is any different. (Perhaps that's the third sentence Cook and Marsh should have written.) 

Fortunately, the giant crab is pretty slow, moving at 60'(20'), so all but the most heavily encumbered adventurers should be able to flee easily -- unless they encounter it in the water, which might well give the crab an edge. Giant crabs are also a bit skittish despite their initial eagerness to attack, with a morale score of 7. Apparently if their prey puts up a stiff fight, they're fairly likely to scuttle away to await an easier meal. 

In outdoor aquatic and coastal environments, you might encounter as many as six giant crabs at once, and if you do, I'd suggest you turn and march briskly in the opposite direction. They have no assigned Treasure Type, so unless there's some incidental loot nearby, you'll probably have nothing to show for a very tough fight. Of course, they're probably pretty good eating, and a lot of it, so they conceivably could be hunted to replenish rations in the field or to drag back to civilization to sell to wealthy gourmets. Curiously, there is also a Number Appearing listed for dungeons, 1-2, which might imply finding them in caves along sea coasts or underwater grottoes, or perhaps even dungeons with underground lakes and streams. That'd be quite a nasty surprise for dungeon-delving adventurers to stumble upon!

I really do like the concept of the giant crab, because it fills a niche of something for PCs to encounter on rocky beaches and their early underwater adventures, once they get some water-breathing spells or magic items. I just think its stats are a little out-of-whack. A damage range of 1-4 or 1-6 points per attack would be more in line with other monsters. Since pincers are made for gripping and holding, you could have it grab and hold on a roll of 19-20, inflicting damage automatically each round after until the crab is killed. It might just hang onto any grabbed prey if its morale fails, dragging it away to its lair to finish off at its leisure. That would actually explain the relatively shaky morale of such an explicitly ravenous creature, too: it aims to grab a meal quickly, and succeed or fail, its instinct is to retreat soon after it attacks.

There's some added potential in the giant crab for modification into other giant crustaceans. Reduce the AC a couple points, add a swimming movement of 120'(40')-ish, and you've got a pretty solid giant lobster or crayfish. You could also shrink it down a bit, reduce AC, HD, and damage by half or more, and call it a "large crab" or use it to represent juvenile giant crabs, either as a challenge for low-level characters or a nuisance for mid-level ones. Finally, there are also land crabs in our real world, so there's absolutely no reason a fantasy world couldn't have giant land crabs, and there's no need to mess with the stats of the standard aquatic variety at all.