Most semi/megabeasts, and most DF creatures in general, have a strong basis in myth and therefore a strongly defined "personality." Not bronze colossi. Therefore, I suggest that either:
1.) Bronze colossi gain more characterization (possibly from a Threetoe story, until Toady One gets around to programming the relevant stuff in).
2.) Bronze colossi are replaced by the following colossi:
(Warning:May contain metaphors that make little sense.)
Iron Colossus
A massive faceless automation with glowing ruby eyes. It is animated by fell magic and lives only to kill.
An iron colossus is incredibly good at killing. It is similar to current bronze colossi. They accept no help from any other living being, slaying on sight everything from cavies to cloens.
Steel Colossus
A broad, massive steel automation with glowing blue, metal eyes. Its hands are like axes, its fists are like hammers, and it strives for glory in battle.
A steel colossus is a dwarf-shaped statue. Its hands are sharpened, so it can karate-chop with deadly force. They kill mighty and dark creatures, so as long as there are frequent zombies, FBs, goblins, and so forth visiting your fort, a steel colossus can be a good thing. If it gets bored, though, it might decide that dwarves are fairly good targets, and...well, there's a reason most forts strive for steel gear. As long as the dwarves are not the most ideal opponents, they tend to travel with steel colossi, like wolf cubs following their parents on a hunt.
Bronze Colossus
A massive, greedy automation with glowing emerald eyes. It takes what it wants and is not stopped by lesser beings.
A statue that comes to your fort, steals some of its most valuable items, and leaves...with a trail of dead dwarves in its path. When diplomacy is implemented, it will try to make you give it the items before rampaging. It might be aided by a group of human mercenaries.
Wood Colossus
A slim, massive wooden automation with pointed ears and glowing coral eyes. It defends all nature with spearlike splinters flung from its palms.
Wood colossi are made of...some kind of wood that probably varies from colossus to colossus. They will leave your fort alone unless you cat down lots of trees, kill lots of elves/animals, etc. Elves tend to side with wood colossi; a wood colossus's home is to elves like a doghouse is to a mouse. Its most notable weapon is the "spearlike splinters" it shoots at passing dwarves.
Obsidian Colossus
A massive bloodstained automation made of obsidian with glowing opal eyes. It leads armies to battle, not caring whose blood is spilled as long as blood is spilled.
Obsidian colossi are to goblins as steel ones are to dwarves. They slaughter massive numbers of creatures, any that they see. Goblins and sometimes others gather around them like jackals to lions, allowed to live as long as they slay beasts in the colossus's name.
Copper Colossus
A huge copper statue with glowing yellow jasper eyes and pointed ears. It sneaks into fors and towns, silent as a shadow, to steal their valuables.
A giant, copper kobold thief. Possible difference: Instead of picking locks, it breaks down the door. I don't recommend it, though. Maybe it camps out, snatching valuables every so often until it's noticed, and then it tries to retrieve its stash and run. Being huge and made of copper, it will fare better than most kobold thieves. Kobold settlements spring up around copper colossus lairs like metaphors in writing.
Maybe these would be castes of a "colossus" creature...hm...
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I would like your thoughts. Although it would be cool if my ideas for colossus castes were taken, I'd be just as happy to see DF bronze colossi get a bit more defined.