SCP-354 is a pool of red liquid in northern Canada — resembling blood but not biological blood — classified Keter for the extreme difficulty of containing it. In the article it is commonly called the "Blood Pond." The pool periodically disgorges hostile anomalous entities, most of which are so dangerous that immediate termination is required.
The heart of the horror is an output with no foreseeable end. The impossibility of predicting what the pool will release, when, or how much turns containment itself into an endless war of preparation. With its source impossible to see into and threats welling up again and again, the dread is kept perpetually alive.