15: Boreal Abyss

Campaign

Waves: 5

Starting Energy: 2000

Lives: 20

This is a boss stage where you'll have to deal with Haxor himself. One important rule about this map is not to invest in a single powerful tower. You'll learn why later on. For starters, you have to defend the northwest and southwest checkpoints. Enemies will be coming in from the entrances on the eastern side of the stage. You can place two infantry towers on both sides of the checkpoints then scatter different towers in the other slots.

In the third wave, Haxor will join the battle and will occassionally freeze four towers at the same time, kill random soldiers (or heavily damage your hero) or worse, destroy any tower instantly. This is the main reason why you shouldn't invest your energy on a single tower. He chooses his targets randomly but it's safe to say that any tower is at risk. You can interrupt him by hitting him with an airstrike or tesla coil zap. This will stun him for a few seconds as well, giving you much needed breathing space to re-establish your defenses. You have to weigh the pros and cons of stunning him or not. He'll continuously annoy you with his attacks but you also take into consideration whether you'll need the tesla charge or airstrike to get you out of a bind. Fortunately, you don't have to worry about many airborne units like the pesky wasps so you just have to keep your towers up and running. To be safe, keep upgrading your towers to at least LV2 to ensure that you'll be able to whittle down the enemy numbers before they get to your soldiers. You don't necessarily need to upgrade the infantry towers at this point.

Veteran

Waves: 6

Starting Energy: 1250

Lives: 1

You can only use infantry and laser towers for this mission. Similar to the campaign setup, place one infantry towers near each checkpoint then litter the other slots with laser towers. Consider upgrading the laser towers first to LV2 once you've filled the other slots already. Once you've upgraded all of the towers to at least LV2, consider specializing at least two towers, especially those that can cover at least two enemy spawn points within their range. You don't have to worry about Haxor so it's okay to invest on fully upgraded laser towers as well. The last wave will consist of several icers so take care of them all at once using your tesla tower. You don't need to upgrade the infantry towers either.

Spec Ops

Waves: 1

Starting Energy: 1750

Lives: 1

Place at least one infantry tower on each checkpoint then create at least two LV2 laser towers near the spawn point. You have to specialize these, preferably to a quad-beam tower. This mission is pretty manageable without using reinforcements or airstrikes but be careful when several icers appear. They will be preceeded by wasps which can be pretty hard to stop if your towers are frozen. The wave is quite short so don't hesitate using a tesla coil charge once the arctic crusaders appear. Place some additional laser towers and MG towers near the checkpoints and upgrade them to LV2 at least. This should be enough to take out the wasps, as long as there are no other ground troops moving with them.