Sinister force existing to the North where the monster lurks (8)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

Reversal (to the North, in a down clue) of LIVE (existing) + NESS (Loch Ness, where the monster lurks). Hard to believe that ‘evilness’ is really a word, when ‘evil’ does the same job, but it is