A large pile of seemingly unguarded coins lies before you.
Metallic Ooze CR 6
Speed 20 ft., climb 10 ft.
Melee slam +7 (1d8+4 plus 1d6 acid plus poison)
Space 10 ft.; Reach 5 ft.
Special Attacks irritating fumes
If a metallic ooze is subjected to a heat or fire effect, it emanates a cloud of semi-transparent vapor that irritates the eyes and respiratory system of living creatures within a 10-foot radius. Affected creatures must succeed on a DC 21 Fortitude save or take 2d6 points of acid damage initially and suffer a -2 circumstance penalty on attack and weapon damage rolls for 3 rounds. The cloud disperses in 1d4 rounds and can be affected by wind. The save DC is Constitution-based.
Treasure double standard
A metallic ooze appears as a 9-foot blob of protoplasm of varying hue and color, and come in a variety of sizes and colors: gold, silver, platinum, copper, brass, or bronze. Regardless of the color or size, metallic oozes resemble large piles of coins. The oozes use their appearance to lure would be treasure hunters to their doom. Because of this, they are sometimes referred to as hoard oozes. Its form is coarse and rough giving it the appearance of piles of coins. A metallic ooze can flatten its body in order to squeeze through spaces and cracks where it normally could not go.
A metallic ooze can be found virtually anywhere, though it tends to inhabit dungeons, ruined temples, castles, and other buildings where treasure seekers seem to enjoy perfecting their craft. From a distance of 30 feet or more, a metallic ooze resembles a pile of loose coins (of whatever type its coloration most closely resembles). A creature can attempt a DC 20 Perception check to notice the ooze for what it is. This monster does not collect treasure, but the remnants of living creatures that meet their demise at the hands of this creature are often found scattered about its lair.
A metallic ooze lies still until it detects a potential meal within range. It then forms a pseudopod and pummels the opponent. Creatures killed by a metallic ooze are devoured. While a metallic ooze can cling to walls and ceilings (and often does drop on unsuspecting prey), it prefers to wander dungeon corridors and such on the ground, often waiting in one spot until living prey wanders too close.
Metallic Ooze from the Tome of Horrors Complete, Copyright 2011, Necromancer Games, Inc., published and distributed by Frog God Games; Author Scott Greene.