Exodus: Creepy Time

Legit Way:
For some reason this took me a while with many retries, I couldn't get it right.
Usually on the game you unlock a new character and you use it for the next level because it suitable better but in this case, previous level 4th you unlock the Paladin, which has a main attack with two fire circles. They do nothing and he is VERY slow.
I've found better to use the Gnome, with his three upgrades, focusing on increasing speed, whenever you are able to pick it (since the upgrades are selectable in between 4 random). That is because at almost 2 minutes of the final boss level appearing a new enemy that looks like a green gnome with pointy ears will show up and they are VERY fast. If your movement is not up to speed, you will be touched by them several times and probably die in 15-20 seconds. That is why you need speed.
Hope this helps

Easy Way:
Go to options and enable infinity health