So my suggestions would be adding:

Water:"Again that water!" would be the reaction that the knights would express becoz:
Water would slow you down by 15% noted by a effect called "Wet!"
Water would slow you further the deeper you went in going like this 15% - 20% - 25% and would finnaly stop at 30%
A good thing about water is that enemies are affected too,Constructs wont enter water becoz they would rust and Explode...so they wont enter!

Bad Water imagination on aurora isles :http://s28.postimg.org/dctbhngy5/Untitled.png

Lava:Entering it would inflict you with fire + wet!
The lava wouldnt damage you but instead the fire effect that would be given to you!
Enemies including Slag walkers + Fire slimes would get healed in it...

Bad lava imagination in FSC :http://postimg.org/image/gc5a1vwqx/

New levels and stages:

Aurora island - Watery Dangers
It would consist of aurora islands connected with Iron bridges that have ponds of water everywhere...
Enemies that would spawn would be gremlins,slimes,Mini enemies,Lumbers(not near water but instead on those mini arenas) and undead(if the level is undead based) http://postimg.org/image/536z0pqbz/

Flaming Forest -Burning Witness
It would be a flat area with bumps and tress everywhere...there would also be a river of lava and there would be around 1-2 arenas in it!
Monsters that would spawn could include Slag walkers,Oilers,Big oilers,Slime turrets(fire version) and Fire lumbers!

http://postimg.org/image/vc50zm44d/

Deadlight Plains - Haunting lands
Would consist of A town connected to a graveyard like area.. the town would be a friendly area with some knights and a special vendor,and the graveyard would be the hostile area...There would be more phantom spawns and more zombie spawns..also in one arena you would have to fight a trojan + all 6 kinds of zombies in 1 arena!

http://postimg.org/image/vsx4oetv7/