Dorian Hawkmoon has been one of the last continental warlords to resist the iron heel of the armies of Granbretan. He is, though, finally taken prisoner and has the evil jewel implanted in his skull by the forces of the Dark Empire when he is taken back to Londra. In turn he is sent out to infiltrate the last stronghold of opposition - that part of sourthern France called the Kamarg, where Count Brass is holding out. There he is rescued from the power of the Jewel, only to lose his new love, and then to see the Castle Brass transmitted into another dimension as it escapes the final destruction of the all-conquering Granbretanians. Somewhere along the way (and we're not half-way in yet) he discovers that the mysterious Runestaff has a purpose for him.
Moorcock wrote these novels in the 'sixties to help finance New Worlds and wrote them quickly, but it is not obvious. And the tricks he has used help to drive the story on, but also underpin it, starting with the reversal of making Granbretan the villain of the piece, and Londra the centre of the spiderweb of evil, and King-Emperor Huon the evil spider. On the other side Hawkmoon, Duke of Koln, could be one of Rider Haggard's heroes unspoiled by excessive introversion or doubt. Then, there is a satisfying appearance and disappearance of characters - as they seem to switch allegiance, and likewise weapons and craft don't last overlong. Hawkmoon escapes from the Kamarg on a giant flamingo, for instance, only for it to be shot down by a hunter who will become his friend. The Granbretanians, meanwhile, will persue him from their slow and ungainly ornithopters. For this is the far future where gothic science meets mutant beast in a new Dark Age.
How far all this fits into Moorcock's Tale of the Eternal Champion I can't say, but on its own it stands up as "a good read", and on that I recommend it.