Here's something for you - not megabeasts, but certainly entertaining. Clockwork cavern crawlers!
Brass Beetles have big stabby horns.
Copper Crustaceans have snatching claws.
Silver Scorpions have snatching claws, as well as a tail full of liquid mercury.
Tin Termites have acid bites that cause necrosis - and aggressive rusting in Iron Men and Bronze Colossi!
[CREATURE:ELEMENTBEAST_BEETLE_BRASS]
[NATURAL_SKILL:DISCIPLINE:1]
[NOPAIN]
[DESCRIPTION:An automaton of brass, built in the shape of a beetle by some ancient artisan. It clicks and clacks as it moves and has gems for eyes.]
[NAME:brass beetle:brass beetles:brass beetle]
[CASTE_NAME:brass beetle:brass beetles:brass beetle]
[CREATURE_TILE:66][COLOR:6:0:1]
[ALTTILE:225][COLOR:6:0:1]
[LARGE_ROAMING]
[CRAZED]
[GENERAL_MATERIAL_FORCE_MULTIPLIER:3:2]
[BIOME:SUBTERRANEAN_CHASM]
[UNDERGROUND_DEPTH:2:3]
[FREQUENCY:20]
[DIFFICULTY:2]
[POPULATION_NUMBER:15:30]
[NOPAIN][EXTRAVISION][NOBREATHE][NOSTUN][NONAUSEA][NOEMOTION]
[NOTHOUGHT][NOEXERT]
[NO_DIZZINESS]
[NO_FEVERS]
[BUILDINGDESTROYER:2]
[LARGE_PREDATOR]
[NO_DRINK][NO_EAT][NO_SLEEP]
[NOT_LIVING]
[CANOPENDOORS]
[NOT_BUTCHERABLE]
[NOFEAR]
[ODOR_LEVEL:0]
[SMELL_TRIGGER:10000] cannot smell
[NOBONES]
[BODY:INSECT:2EYES:MOUTH:2WINGS:2HEAD_HORN_NUMBERED]
[EXTRAVISION] eyes are just for decor
[NO_THOUGHT_CENTER_FOR_MOVEMENT]
[TISSUE:BRASS]
[TISSUE_NAME:brass:NP]
[TISSUE_MATERIAL:INORGANIC:BRASS]
[MUSCULAR]
[FUNCTIONAL]
[STRUCTURAL]
[RELATIVE_THICKNESS:1]
[CONNECTS]
[TISSUE_SHAPE:LAYER]
[TISSUE_LAYER:BY_CATEGORY:ALL:BRASS]
[BODY_SIZE:0:0:70000]
[BODY_APPEARANCE_MODIFIER:HEIGHT:90:95:98:100:102:105:110]
[BODY_APPEARANCE_MODIFIER:BROADNESS:90:95:98:100:102:105:110]
[APPLY_CREATURE_VARIATION:HORN_GORE_ATTACK]
[APPLY_CREATURE_VARIATION:KICK_HIGHVEL_ATTACK]
[ITEMCORPSE:STATUE:NO_SUBTYPE:INORGANIC:BRASS]
[ITEMCORPSE_QUALITY:5]
[ALL_ACTIVE]
[APPLY_CREATURE_VARIATION:STANDARD_BIPED_GAITS:2206:1692:1178:585:3400:4900] 15 kph
[APPLY_CREATURE_VARIATION:STANDARD_CLIMBING_GAITS:2990:2257:1525:731:4300:6100] 12 kph
[APPLY_CREATURE_VARIATION:STANDARD_SWIMMING_GAITS:2990:2257:1525:731:4300:6100] 12 kph
[APPLY_CREATURE_VARIATION:STANDARD_CRAWLING_GAITS:2990:2257:1525:731:4300:6100] 12 kph
[STANCE_CLIMBER]
[NATURAL_SKILL:CLIMBING:10]
[SET_TL_GROUP:BY_CATEGORY:EYE:EYE]
[TL_COLOR_MODIFIER:AMETHYST:1:EMERALD:1:AQUAMARINE:1]
[TLCM_NOUN:eyes:PLURAL]
==
[CREATURE:ELEMENTBEAST_SCORPION_SILVER]
[NATURAL_SKILL:DISCIPLINE:1]
[NOPAIN]
[DESCRIPTION:An automaton of silver, forged in the shape of a scorpion by some ancient artisan. Its gemstone eyes glitter in darkness, and liquid mercury drips from its wicked stinger.]
[NAME:silver scorpion:silver scorpions:silver scorpion]
[CASTE_NAME:silver scorpion:silver scorpions:silver scorpion]
[CREATURE_TILE:83][COLOR:7:0:1]
[ALTTILE:36][COLOR:7:0:1]
[LARGE_ROAMING]
[CRAZED]
[GENERAL_MATERIAL_FORCE_MULTIPLIER:3:2]
[BIOME:SUBTERRANEAN_CHASM]
[UNDERGROUND_DEPTH:2:3]
[FREQUENCY:20]
[DIFFICULTY:2]
[POPULATION_NUMBER:15:30]
[NOPAIN][EXTRAVISION][NOBREATHE][NOSTUN][NONAUSEA][NOEMOTION]
[NOTHOUGHT][NOEXERT]
[NO_DIZZINESS]
[NO_FEVERS]
[BUILDINGDESTROYER:2]
[LARGE_PREDATOR]
[NO_DRINK][NO_EAT][NO_SLEEP]
[NOT_LIVING]
[CANOPENDOORS]
[NOT_BUTCHERABLE]
[NOFEAR]
[ODOR_LEVEL:0]
[SMELL_TRIGGER:10000] cannot smell
[NOBONES]
[BODY:SPIDER:2EYES:MOUTH:UPPERBODY_PINCERS:TAIL:TAIL_STINGER]
[EXTRAVISION] eyes are decorative
[NO_THOUGHT_CENTER_FOR_MOVEMENT]
mercury venom
[USE_MATERIAL_TEMPLATE:VENOM:CREATURE_EXTRACT_TEMPLATE]
[STATE_NAME:ALL_SOLID:hardened mercury]
[STATE_ADJ:ALL_SOLID:hardened mercury]
[STATE_NAME:LIQUID:mercury]
[STATE_ADJ:LIQUID:mercury]
[STATE_NAME:GAS:boiling mercury]
[STATE_ADJ:GAS:boiling mercury]
[PREFIX:NONE]
[ENTERS_BLOOD]
[SYNDROME]
[SYN_NAME:mercury poisoning]
[SYN_AFFECTED_CLASS:GENERAL_POISON]
[SYN_INJECTED]
[SYN_CONTACT]
[CE_ERRATIC_BEHAVIOR:SEV:100:PROB:15:RESISTABLE:SIZE_DILUTES:START:400:DWF_STRETCH:4]
[TISSUE:SILVER]
[TISSUE_NAME:silver:NP]
[TISSUE_MATERIAL:INORGANIC:SILVER]
[MUSCULAR]
[FUNCTIONAL]
[STRUCTURAL]
[RELATIVE_THICKNESS:1]
[CONNECTS]
[TISSUE_SHAPE:LAYER]
[TISSUE:VENOM]
[TISSUE_NAME:mercury:NP]
[TISSUE_MATERIAL:LOCAL_CREATURE_MAT:VENOM]
[TISSUE_MAT_STATE:LIQUID]
[RELATIVE_THICKNESS:50]
[TISSUE_LEAKS]
[TISSUE_SHAPE:LAYER]
[TISSUE_LAYER:BY_CATEGORY:ALL:SILVER]
[TISSUE_LAYER_UNDER:BY_CATEGORY:STINGER:VENOM]
[BODY_SIZE:0:0:70000]
[BODY_APPEARANCE_MODIFIER:LENGTH:90:95:98:100:102:105:110]
[BODY_APPEARANCE_MODIFIER:BROADNESS:90:95:98:100:102:105:110]
[ITEMCORPSE:STATUE:NO_SUBTYPE:INORGANIC:SILVER]
[ITEMCORPSE_QUALITY:5]
[APPLY_CREATURE_VARIATION:TAIL_STING_VENOM_ATTACK]
[APPLY_CREATURE_VARIATION:PINCER_ATTACK]
[APPLY_CREATURE_VARIATION:MOUTH_BITE_ATTACK]
[ALL_ACTIVE]
[APPLY_CREATURE_VARIATION:STANDARD_BIPED_GAITS:2206:1692:1178:585:3400:4900] 15 kph
[APPLY_CREATURE_VARIATION:STANDARD_CLIMBING_GAITS:2990:2257:1525:731:4300:6100] 12 kph
[APPLY_CREATURE_VARIATION:STANDARD_SWIMMING_GAITS:2990:2257:1525:731:4300:6100] 12 kph
[APPLY_CREATURE_VARIATION:STANDARD_CRAWLING_GAITS:2990:2257:1525:731:4300:6100] 12 kph
[STANCE_CLIMBER]
[NATURAL_SKILL:CLIMBING:10]
[SET_TL_GROUP:BY_CATEGORY:EYE:EYE]
[TL_COLOR_MODIFIER:AMETHYST:1:EMERALD:1:AQUAMARINE:1]
[TLCM_NOUN:eyes:PLURAL]
==
[CREATURE:ELEMENTBEAST_CRUSTACEAN_COPPER]
[NATURAL_SKILL:DISCIPLINE:1]
[NOPAIN]
[DESCRIPTION:An automaton of copper, forged in the shape of a crustacean by some ancient artisan. Its mighty pincers can shear through armor easily.] Revision: rewrote description.
[NAME:copper crustacean:copper crustaceans:copper crustacean]
[CASTE_NAME:copper crustacean:copper crustaceans:copper crustacean]
[CREATURE_TILE:99][COLOR:6:0:0]
[ALTTILE:128][COLOR:6:0:0]
[LARGE_ROAMING]
[CRAZED]
[GENERAL_MATERIAL_FORCE_MULTIPLIER:3:2]
[BIOME:SUBTERRANEAN_CHASM]
[UNDERGROUND_DEPTH:2:3]
[FREQUENCY:20]
[DIFFICULTY:2]
[POPULATION_NUMBER:15:30]
[NOPAIN][EXTRAVISION][NOBREATHE][NOSTUN][NONAUSEA][NOEMOTION]
[NOTHOUGHT][NOEXERT]
[NO_DIZZINESS]
[NO_FEVERS]
[BUILDINGDESTROYER:2]
[LARGE_PREDATOR]
[NO_DRINK][NO_EAT][NO_SLEEP]
[NOT_LIVING]
[CANOPENDOORS]
[NOT_BUTCHERABLE]
[NOFEAR]
[ODOR_LEVEL:0]
[SMELL_TRIGGER:10000] cannot smell
[NOBONES]
[BODY:CRAB_BODY:2EYES:UPPERBODY_PINCERS]
[EXTRAVISION] eyes are for decoration
[NO_THOUGHT_CENTER_FOR_MOVEMENT]
[TISSUE:COPPER]
[TISSUE_NAME:copper:NP]
[TISSUE_MATERIAL:INORGANIC:COPPER]
[MUSCULAR]
[FUNCTIONAL]
[STRUCTURAL]
[RELATIVE_THICKNESS:1]
[CONNECTS]
[TISSUE_SHAPE:LAYER]
[TISSUE_LAYER:BY_CATEGORY:ALL:COPPER]
[BODY_SIZE:0:0:70000]
[BODY_APPEARANCE_MODIFIER:HEIGHT:90:95:98:100:102:105:110]
[BODY_APPEARANCE_MODIFIER:BROADNESS:90:95:98:100:102:105:110]
[APPLY_CREATURE_VARIATION:PINCER_ATTACK]
[ITEMCORPSE:STATUE:NO_SUBTYPE:INORGANIC:COPPER]
[ITEMCORPSE_QUALITY:5]
[ALL_ACTIVE]
[APPLY_CREATURE_VARIATION:STANDARD_BIPED_GAITS:2206:1692:1178:585:3400:4900] 15 kph
[APPLY_CREATURE_VARIATION:STANDARD_CLIMBING_GAITS:2990:2257:1525:731:4300:6100] 12 kph
[APPLY_CREATURE_VARIATION:STANDARD_SWIMMING_GAITS:2990:2257:1525:731:4300:6100] 12 kph
[APPLY_CREATURE_VARIATION:STANDARD_CRAWLING_GAITS:2990:2257:1525:731:4300:6100] 12 kph
[SWIMS_INNATE]
[SET_TL_GROUP:BY_CATEGORY:EYE:EYE]
[TL_COLOR_MODIFIER:AMETHYST:1:EMERALD:1:AQUAMARINE:1]
[TLCM_NOUN:eyes:PLURAL]
==
[CREATURE:ELEMENTBEAST_TERMITE_TIN]
[NATURAL_SKILL:DISCIPLINE:1]
[NOPAIN]
[DESCRIPTION:An automaton of tin, built in the shape of a termite by some ancient artisan. Its mouth leaks a corrosive acid which melts through flesh, and its gemstone eyes glitter in the darkness.]
[NAME:tin termite:tin termites:tin termite]
[CASTE_NAME:tin termite:tin termites:tin termite]
[CREATURE_TILE:84][COLOR:0:0:1]
[ALTTILE:209][COLOR:0:0:1]
[LARGE_ROAMING]
[CRAZED]
[GENERAL_MATERIAL_FORCE_MULTIPLIER:3:2]
[BIOME:SUBTERRANEAN_CHASM]
[UNDERGROUND_DEPTH:2:3]
[FREQUENCY:20]
[DIFFICULTY:2]
[POPULATION_NUMBER:15:30]
[NOPAIN][EXTRAVISION][NOBREATHE][NOSTUN][NONAUSEA][NOEMOTION]
[NOTHOUGHT][NOEXERT]
[NO_DIZZINESS]
[NO_FEVERS]
[BUILDINGDESTROYER:2]
[LARGE_PREDATOR]
[NO_DRINK][NO_EAT][NO_SLEEP]
[NOT_LIVING]
[CANOPENDOORS]
[NOT_BUTCHERABLE]
[NOFEAR]
[ODOR_LEVEL:0]
[SMELL_TRIGGER:10000] cannot smell
[NOBONES]
[BODY:INSECT:2EYES:MOUTH:2WINGS]
[EXTRAVISION] eyes decorative
[NO_THOUGHT_CENTER_FOR_MOVEMENT]
[USE_MATERIAL_TEMPLATE:VENOM:CREATURE_EXTRACT_TEMPLATE]
[STATE_NAME:ALL_SOLID:crusty acid vomit]
[STATE_ADJ:ALL_SOLID:crusty acid vomit]
[STATE_NAME:LIQUID:acid vomit]
[STATE_ADJ:LIQUID:acid vomit]
[STATE_NAME:GAS:boiling acid vomit]
[STATE_ADJ:GAS:boiling acid vomit]
[PREFIX:NONE]
[SYNDROME]
[SYN_NAME:acid burn]
[SYN_AFFECTED_CLASS:GENERAL_POISON]
[SYN_AFFECTED_CREATURE:ELEMENTMAN_IRON]
[SYN_AFFECTED_CREATURE:COLOSSUS_BRONZE]
[SYN_AFFECTED_CREATURE:ELEMENTBEAST_BEETLE_BRASS]
[SYN_AFFECTED_CREATURE:ELEMENTBEAST_SCORPION_SILVER]
[SYN_AFFECTED_CREATURE:ELEMENTBEAST_CRUSTACEAN_COPPER]
[SYN_CONTACT]
[CE_NAUSEA:SEV:100:PROB:50:RESISTABLE:START:50:PEAK:250:END:500:DWF_STRETCH:12]
[CE_PAIN:SEV:750:PROB:100:SIZE_DILUTES:LOCALIZED:VASCULAR_ONLY:START:50:PEAK:500:END:1500:ABRUPT_START:ABRUPT_END:DWF_STRETCH:12]
[CE_NECROSIS:SEV:5000:PROB:100:LOCALIZED:START:0:PEAK:500:END:1500:ABRUPT_START:ABRUPT_END:DWF_STRETCH:12]
[TISSUE:TIN]
[TISSUE_NAME:tin:NP]
[TISSUE_MATERIAL:INORGANIC:TIN]
[MUSCULAR]
[FUNCTIONAL]
[STRUCTURAL]
[RELATIVE_THICKNESS:1]
[CONNECTS]
[TISSUE_SHAPE:LAYER]
[TISSUE_LAYER:BY_CATEGORY:ALL:TIN]
[BODY_SIZE:0:0:70000]
[BODY_APPEARANCE_MODIFIER:HEIGHT:90:95:98:100:102:105:110]
[BODY_APPEARANCE_MODIFIER:BROADNESS:90:95:98:100:102:105:110]
[APPLY_CREATURE_VARIATION:MOUTH_BITE_VENOM_ATTACK]
[APPLY_CREATURE_VARIATION:KICK_ATTACK]
[ITEMCORPSE:STATUE:NO_SUBTYPE:INORGANIC:TIN]
[ITEMCORPSE_QUALITY:5]
[ALL_ACTIVE]
[APPLY_CREATURE_VARIATION:STANDARD_BIPED_GAITS:2206:1692:1178:585:3400:4900] 15 kph
[APPLY_CREATURE_VARIATION:STANDARD_CLIMBING_GAITS:2990:2257:1525:731:4300:6100] 12 kph
[APPLY_CREATURE_VARIATION:STANDARD_SWIMMING_GAITS:2990:2257:1525:731:4300:6100] 12 kph
[APPLY_CREATURE_VARIATION:STANDARD_CRAWLING_GAITS:2990:2257:1525:731:4300:6100] 12 kph
[STANCE_CLIMBER]
[NATURAL_SKILL:CLIMBING:10]
[SET_TL_GROUP:BY_CATEGORY:EYE:EYE]
[TL_COLOR_MODIFIER:AMETHYST:1:EMERALD:1:AQUAMARINE:1]
[TLCM_NOUN:eyes:PLURAL]