Are you sure [BIOME:ALL_MAIN] is even possible?
Try [BIOME:ALL_LAND] and note that you won't be able to bring the extract with you unless you use a civ that is not dorfs.
WRONG, SIR! On the second count, anyway. I moved them to the "creature_subterranean" file and now Ooze Samples show up. Though I wouldn't have thought of that, so thank you.
However, getting them to spawn is another matter entirely. I may try turning down the frequency of creatures for a specific biome and see if I can get them to spawn for playtesting.
Here's the creature code so far.
[CREATURE:OOZE_INEVITABLE]
[NAME:inevitable ooze:inevitable oozes:inevitable ooze]
[TILE:176][COLOR:3:0:1][ALTTILE:177]
[MODVALUE:3]
[LARGE_ROAMING][FREQUENCY:100][DIFFICULTY:2]
[POPULATION_NUMBER:1:12]
[CLUSTER_NUMBER:1:12]
[EXTRACT:ooze sample:3:0:1]
[EXTRACT_VALUE:10]
[EXTRACT_PARALYZE]
[CURIOUSBEAST_EATER]
[CURIOUSBEAST_GUZZLER]
[BONECARN]
[LARGE_PREDATOR]
[LIKES_FIGHTING]
[GENPOWER:6]
[PETVALUE:750]
[GRASSTRAMPLE:20][NATURAL]
[PREFSTRING:amorphous bodies]
[PREFSTRING:rugged persistence]
[CANOPENDOORS]
[NOT_BUTCHERABLE]
[NOPAIN][EXTRAVISION][NOBREATHE][NOSTUN][NONAUSEA][NOEMOTION]
[SEVERONBREAKS][NOSKULL][NOSKIN][NOBONES][NOMEAT][NOTHOUGHT][NOEXERT]
[BUILDINGDESTROYER:1]
[NOSMELLYROT]
[NOFEAR]
[BODY:BASIC_1PARTBODY_STANCE]
[BODYGLOSS:OOZE]
[BODYGLOSS:OOZE2]
[SIZE:10]
[MAXAGE:900:1000]
[ATTACK:MAIN:BYTYPE:MOUTH:absorb:absorbs:1:6:BLUDGEON][ATTACKFLAG_CANLATCH][SPECIALATTACK_INJECT_EXTRACT:50:100]
[CHILD:1][CHILDNAME:inevitable ooze spawn:inevitable ooze spawn][LITTERSIZE:1:2]
[NO_SLEEP]
[LOOSE_CLUSTERS]
[ALL_ACTIVE]
[BIOME:ALL_MAIN
[STANDARD_FLESH]
[BLOODTYPE:SLIME]
[HOMEOTHERM:10067]
[LAYERING:100]
[SWIMS_INNATE][SWIM_SPEED:5000]
[CANNOT_UNDEAD]
[MUNDANE]
The idea is a horrifying, slow-moving omnivorous horde that (once I can tweak the spawn settings and get it to show up reliably/when desired) appears to lay waste to your food. Magma and chameleon varieties are planned for after I get this one working.
Edit: RELATIVE SUCCESS!
There are more which are outdoors, but they refuse to loot my food/drink stockpiles. They have [NOFEAR], so this is peculiar. Maybe [RECKLESS] is needed. Will run this game a little further to see what happens.