George R.R. Martin, author of the books that were made into the cult TV saga ‘Game of Thrones,’ has promised a ‘grisly death’ to two donors who give $20,000 to a wolf sanctuary.

In a video and statement on the crowdfunding site, the author calls for donations to the Wild Spirit Wolf Sanctuary, a refuge near the southwestern US city of Santa Fe. ‘I've always been fond of wolves,’ he said, noting that ‘US wolf populations hit critical lows during the twentieth century.’

The money raised - the overall goal is set at $500,000 - will also support The Food Depot charity, which provided more than 500,000 meals to people in need last year. The US novelist calls for donations starting at just $10. But at the highest level, $20,000, a man and a woman will each be given the chance of having a character - ‘lordling, knight, peasant, whore, lady, maester, septon, anything’ - named after them in Martin's upcoming ‘Song of Ice and Fire’ novel, according to Prizeo.

‘You will certainly meet a grisly death,’ the site warned. As of Friday evening at 9:00 pm (0100 GMT Saturday) more than $280,000 had been raised - including two donations of $20,000 each claiming the character-naming prizes. Other rewards offered for smaller-scale donations included t-shirts, books and a drawing to visit the writer and the wolves. Since its debut in 2011, the HBO drama based on Martin's best-selling novels about a struggle for power between feuding clans in seven mythical kingdoms has won a devoted global fan base - President Barack Obama reportedly among them - to establish itself as the star of the US cable channel's stable.

The series has wowed critics with its densely-layered plot, lavish production values and a readiness to kill off, invariably in gruesome fashion, protagonists who had hitherto seemed integral to the show.