Erik (Robbins) is a Viking who cares, a New Man in a horned helmet and a filthy sheepskin. But he's not very good at it, and while debating the pointlessness of sacking villages just to raise funds to sack villages with a grim-faced potential rapee, he manages to accidentally kill her. Grief stricken, he rounds up some chums and sets off to Askgaard to get the Gods to end the Age Of Ragnarok, which started when a wolf swallowed the sun and involves relentless killing until there's no-one left.
As you'd expect, Erik The Viking has all the Pythonesque ingredients that the ex-members have jammed into their films over the last decade. A central joke that appeals mainly to academics; a peasantry that is literally revolting; a cartoon style special effects sequence involving a monster; John Cleese being tetchy; a main character who triumphs through absurdly logical naivety; and dialogue, characters and situations that serve no function other than to raise a laugh.
Provided that last point goes far enough, up until Erik that was all you really wanted or needed in a Pythonesque movie; even Terry Gilliam's Jabberwocky scraped by on its pointless silliness. But when the off-the-cuff-stupidity is this thin on the ground, the formula suddenly runs out of steam.