CR 11; XP 12,800
N Colossal Ooze
Init +0; Senses blindsense 60 ft., scent; Perception +0
AC 22, touch 2, flat-footed 22 (+20 natural, –8 size)
hp 150 (12d8+96)
Fort +12, Ref +4, Will +4
Defensive Abilities diffuse, elemental reactivity; DR 10/—; Immune acid, cold, death, disease, electricity, fire, ooze traits, petrificiation, polymorph
Weakness repelled by water
Speed 30 ft., burrow 10 ft.
Melee dissolve (10d10)
Space 30 ft.; Reach 30 ft.
Special Attacks dissolve
Str 10, Dex 10, Con 26, Int —, Wis 10, Cha 1
Base Atk +9; CMB —; CMD —
SQ bore through stone
Treasure standard (nuggets of pure metal)
Bore Through Stone (Ex) A namesake ability of a mining ooze allows it to dissolve solid, non-magical stone, at the rate of one 5-ft cube per hour.
Diffuse (Ex) A mining ooze is enormous blanket of thin slime, acting similarly in some ways more like swarm than solid entity. It can slide over difficult terrain, obstacles, and creatures of any size without hindrance, and it can move into spaces much smaller than its actual size, while acting as a difficult terrain for any creatures moving through its space. For example, it can move into tunnels as long as it retains continuity and fills a total of 36 5-ft. cubes. Mining ooze is too soft and malleable to be affected with combat maneuvers, suffers no damage from falls, and cannot be trapped, buried, and crushed under avalanches and seismic events.
Dissolve (Ex) A mining ooze makes no regular attacks, instead, it automatically deals listed damage to all creatures and unattended organic objects within its space at the end of its move. Creatures and objects reduced to 0 hit points are dissolved and absorbed by the ooze, effectively disintegrating them.
Elemental Reactivity (Ex) While a mining ooze is immune to damage from acid, cold, electricity, or fire, it reacts in certain ways to them. Electricity staggers it for one round, but also attracts, making it move toward the source of electricity until the end of its following turn (barring other stimuli). Cold solidifies, increasing its coherence and healing 1 hit point per three damage it should inflict, but also reduces range of its blindsense to 10 feet until the end of its following turn. Acid attracts mining ooze while suppressing its scent until the end of the following turn. Fire heals it and staggers. When multiple effect attract a mining ooze at the same time, it moves toward the strongest one.
Repelled By Water (Ex) A mining ooze avoids contact with fresh water. When submerged, it seeks the shortest route out of the water, and it avoids squares containing open water. Despite this revulsion, water does not seem to cause any short-term harm to mining oozes, and no one managed to keep one submerged for long enough to find if it has any long-lasting effects on them.
Mining ooze is somewhere between being a force of nature, an underground environmental hazard, and a living, though extremely dangerous digging tool. The origins of mining oozes are unknown—some dwarven sages speculate they come from the farthest depths of the earth itself, where heat and lack of air is lethal to living creatures. A few brave (or crazy) dwarven crews attempted to harness the stone-dissolving ability of mining oozes, hence the name. They used water and elemental magic to crudely direct the creatures into right places. There is an issue with reclaiming nuggets of pure metals that get embedded in a mining ooze, though, as it requires killing those enormously resilient creatures, which is not a trivial task even for a dedicated crew of dwarven miners.
Note: The creature's CR reflects is resilience and ability to deal mass damage in direct, unrefined combat. It's mindlessness combined with elemental reactivity can be used against it quite creatively, allowing for easier victories than its CR would suggest.