The Taylor Glacier in Antartica’s dry valleys sports a blood-red waterfall some five storeys tall. As described at Atlas Obscura, the source is a lake that was trapped by the ice some 2 million years ago. The lake’s water is very saline, which I presume is why it didn’t freeze, and rich in iron, which produces the striking colour. The falls are the result of a fissure in the glacier, which allows the water to ooze out. And perhaps most incredible of all, the lake is host to a colony of microbes still living there, without light, without (much) heat, isolated from the rest of the world for all that time.
The image of a glacier in a frozen landscape oozing blood is tremendously evocative. Imagine in a place where the predominant colours are white, black, and grey, suddenly against a huge chalk-coloured wall of ice there is a brilliant red gash. Equally evocative is the idea of a glacier as something that can keep something hidden for millions of years, literally for so long that there is no record or memory of it being there.
There are obvious connections to H. P. Lovecraft’s At the Mountains of Madness, or to movies like The Thing (based off John Campbell’s 1938 novella Who goes there?). In each of these, something has ended up covered by ice by more-or-less accidental circumstances, what if something was deliberately sealed beneath a glacier? In a fantasy setting, could some ancient creature or culture be deemed so wicked or dangerous that magical or divine powers bury it under the ice? Now the ice thins and a danger long forgotten returns once more – would you need to find means to defeat it, or to replace the ice over it and bury it once again?