Planar Bestiary
Coming in out of the rain, cloak sopping wet, isn't normally dangerous. But if the storm was tinged with influence from the Elemental Chaos (a dimension where the Planes of Air, Fire, Water, Earth, and other planes violently mix), that cloak that doesn't seem to want to dry could be a puddle weird waiting for their chance to spread chaos.
The storms that roll through the Elemental Chaos are sometimes so fierce that they roil the Ethereal and worlds of the Material Plane that it connects to. This kind of influence might cause a regular storm on a Material Plane world or increase the vigor of a storm already in progress. But sometimes elementals of various sorts spill across that gap. One of the most dangerous is the puddle weird, because it's not immediately obvious what they are, and because of the effect their touch has on flesh.
As a being of elemental animation, a puddle weird doesn't require air, food, drink, or sleep.
Motive: Spread chaos and mischief across the multiverse
Environment: Anywhere violent storms rage or have recently raged, alone or in the company of other elementals
Health: 12
Damage Inflicted: Minor wound (3 points)
Movement: Immediate
Modifications: Disguise (as normal water when motionless) as level 5; Speed defense as level 5 due to tiny size
Combat: The puddle weird condenses a fist of water to batter foes. Targets that take damage must succeed on a Might defense task, or begin absorbing moisture from the atmosphere, swelling their flesh with water. Any time the swelling creature takes physical damage from any source, they take an additional minor wound (3 points). The victim can attempt another defense task each round to end the swelling and discharge some of the water. When the effect ends, the target is immune to the effect for a day; however, their puffy, bloated form does not fully return to normal until after their next 10-hour recovery.
If the puddle weird takes cold damage, they partially freeze, and they can't move from their spot until after their next turn.
A puddle weird is immune to electricity and poison attacks.
Interaction: Puddle weirds are not particularly intelligent, but they can communicate in the ancient language of elementals (Primordial). They are not motivated by what's important to living things; they want to find new places, to deliquesce living beings, and spread mischief.
Use: The jar of liquid at the edge of the bar on a hot day seems ideal for quenching one's thirst. A puddle in a rainstorm formed more quickly than seems reasonable. An explorer's cloak never seems to get dry.
GM Intrusion: All the liquids carried by a character (including magical potions and elixirs, if any) burst from their containers and join with the puddle weird, restoring the creature's health.