Sand Slime (5e Hazard)
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Related to green slime, this grainy, viscous ooze is encountered in patches covering hundreds of square feet. It looks exactly like wet sand. A successful DC 20 Wisdom (Perception) check or DC 15 Intelligence (Nature) check reveals its true nature. Sand slime is sticky and absorbs the slightest moisture, which withers and kills most small animals (which the slime then absorbs). Creatures that step into sand slime, or start their turn in it, take 5 (1d10) necrotic damage and become restrained. A restrained creature or a creature within 5 feet of the restrained creature can use its action to make a DC 12 Strength (Athletics) check, breaking free on a success.