Once you finish VigkVagk's missions, load the completed data for Inphyy. You now have access to a new level.
Before you start this mission, you will most definitely want to reply older missions until you reach level nine.
Mission 7. Another World.
At the start of this mission you will be instructed to find the King of the Night.
The King of the Night is in the North most area of the map. In order to effectively defeat the King of the Nights you will need to equip a Deadly Armband. That item is dropped by his minions, which are quite prevalent on this level. However, there is actually a fairly decent chance that after killing every enemy in this level you still do not get the item (it happened to me a couple times). Since the larger portion of his minions are in the area with him, I would suggest running directly to the end of the level and killing all the minions around him. If you do not get the drop, then restart the level.
To defeat the King of the Nights, rely solely on your level nine combo
Do not fight him head on. Try to only get as close as you need to in order to hit him. After a few decent hits, you will defeat him.
Congratulations! Now you really have finished Ninety Nine Nights!