Ideas for LoZ fangame Bosses

am remakeing my game on a Game maker format and it is very hard and confusing but i
will not give up yet. I ask you zelda fans this:
What will be a great bosses for these 5 places

Forest Cavern
Underground Castle in the Mountains( Mt. Grotto)
Water Tower(has 8 basesments lol)
The light in the forest.(Them)
and
Black Tower


PS: this a 4 player zelda game.
(someone brought up something called a sharquoi.)