Overboss looks like a fun idea. Coming from the same team that gave us Legend of Keepers, it has you emerge from the underworld to take over the overworld. This is actually a digital version of the board game of the same name, which was from the same people that made Boss Monster (a favourite of mine).
You go through grabbing tiles to place on the map to build it up, then you get to place down monsters or a mini-boss and continue building up the world with various tiles giving different point bonuses. Placement seems to be key here and it will have a competitive element to it with you being able to face off against others online as you each compete to be the Overboss.
No release date is being given just yet.