Level 13 – Halls of the King
Which king, specifically, I have no idea. There are a few viable approaches to this level, depending on whether you want your primary killzone to be the road leading to the first high ground, or the enclosed area immediately outside the gem cave. For the first, you should be building your friend the Chilling Crypt on both high grounds. For the second, Burning Temples will probably work better.
Be sure to cover all of the mana pools – a Chilling Crypt on the mana pool halfway down the main road can be absolutely devastating. There’s a tile of rock near the entrance where you can set up a ninja-proofing Temple as well. Between the ninja-proofing Temple, the mana pool Chilling Crypt, and a Chilling Crypt on the first high ground, the avenue will become a deathtrap. The two tiles of rock flanking the entrance to the alcove containing the second high ground should also have temples mounted.
Even if you plan to do most of your killing in the main avenue, defend the enclosed area as much as you can – that’s where you’ll be getting the majority of your ninja kills.
Level 14 – The Secret Passage
As you can see, there is indeed a secret passage connecting your gem caves.
Why it was felt necessary to name the level after this feature is beyond me, because if you`re doing it right nothing will ever set foot in there.
While Burning Temples seem like the obvious choice for the high ground outside each cave, Chilling Crypts are actually better – they`ll be able to hit both the approach to their gem cave, and the approach to the other, making them doubly useful. The outer two high grounds, near the entrances to the map, make good mounts for ninja-proofing Temples.
Apart from the high ground and mana pools, the best spot for building towers on this map is the wall of snow in the northwest corner of the map – Crypts built here will be able to counter enemies on both sides of the map. You will also need a cluster of towers around the entrance to the southern gem cave, since there will be ninjas.
Level 15 – Battle City
Battle City, is a level that does not necessarily reward any one strategy. The level is covered in high ground, meaning that you can use a variety of tower types and employ any number of possible strategies, many of which will work. Play to the strengths of the skill tree you specialize in, devise a strategy that makes the best use of your favoured towers, and then dismiss this strategy and just build Chilling Crypts everywhere, because never before has there been a level so vulnerable to your friend. A few ninja-proofing Temples at the northern end of the map and the enemy will collapse.