Crystalline oozes that resemble needle-tipped serpents made of ice, freezing flows are born where the ice of the Elemental Planes meets the air of the Material…and grows hungry. With their ability to remain dormant for so long they are as much traps as they are creatures, and their single-minded hunt for warm-blooded food means they show their prey no mercy. A friend downed by a freezing flow is likely dead if you cannot reach him in time…but once sated, at least it will have no more interest in you.
A particularly cold winter sends the city’s ratfolk scurrying into their home of last resort, the sewers…only to come running out again. The arctic cold has found its way even there, and brought with it a freezing flow that hunts the furry humanoids. They seek help from adventurers, and intimate that in their flight they have uncovered a secret down below as well.
An ice devil encourages freezing flows to nest in the tunnels below his fortress, feeding them with scraps (that is, worn-out slaves). While even the largest (Advanced) freezing flows cannot offer much challenge to a typical gelugon’s enemies, the caverns are designed to bring the sounds of even a minor skirmish echoing up to the guard posts, alerting the entire complex. Using fire to end the encounter quickly only causes jagged icicle spikes to rain down on interlopers.
A mage experiments with scribing spells onto crystals, coaxing more uses out of the spell energy than she would from a single scroll. One of her experiments involves inserting a core of elemental ice into a large geode; she believes the extreme cold will bind the spell energy even longer. When she takes time off from her experiments to deal with a band of troublesome adventurers, the ice core stirs, brought to life in this world as a freezing flow. It will eagerly feed on whoever opens the door next—the mage or her meddling foes.
—Pathfinder Bestiary 4 115
For fantasy fans with long memories, there are shades of Finder Wyvernspur in that last seed.