Seek the Saboteurs

This scrap of paper seems to have been left behind accidentally by the Dark Iron invaders.$B$BWhile the plans are complicated and written in some form of coded Dwarvish, the signature at the end - "Coren Direbrew" - is clear enough, as is mention of the Grim Guzzler deep within Blackrock Depths. You should seek out the instigator and put an end to these raids.