You can't simply 'avoid' him, since you can't use the the portal down to Shard in combat. The only way to not fight him would be to run past, leave the game, bring in a diff char, kill him, return, and THEN be able to use the portal down to Shard after the area is clear. Karl clearly belongs a couple dungeons up, he's a lot tougher than Shard is. Oops, now Shard gets harder. Sorry, folks.