The area around at the Eternia Crystal is more open than it is on the previous three maps. All four enemy pathways end with a gentle descent before they converge at the core. The more enclosed north and south paths give the Dark Elf Mages cover as they summon Skeletons, revive them and heal themselves and other enemies. Their behavior can lead to serious traffic jams at the two right-side chock-points (relative to the core). Multiple mages can group up behind other enemies to endless heal them, as they and their skeletons break down the players' physical barriers. If the front-line crowd cannot be damaged fast enough or the mages are not killed first, the horde will eventually break through and annihilate the core.
There are ways to prevent these seemingly invincible enemy bottlenecks without overwhelming DPS the mages's healing cannot keep up with. Lightning Towers can stun-lock and kill most of them, only leaving the ones immune to lightning left. Non-physical defenses (auras, traps and beams) placed in front of walls can also kill or cripple them before they start summoning skeletons.
When the final wave of the Campaign is reached, the players are warned that it is also the "Boss Wave." Once this wave ends (initially), anyone who died in combat when Hardcore Mode is enabled can respawn. All players and the core are fully healed, regardless of difficulty. The boss will then appear after a countdown. The other enemies will resume spawning and will not stop spawning until the boss is defeated.
Main Article: Demon Lord
The Demon Lord is an enormous threat to physical defenses. Though he prioritizes heroes, his attacks can seriously damage or destroy towers unexpectedly, either from his two swords or deadly fire trails that chases after a target. The latter is telegraphed when the Demon Lord slowly raises up and holds both swords together. Towers and heroes can attack the four Tesla coils surrounding the core to stun the boss.
- When the player is choosing where to summon a selected defense, if its ghost image overlaps where the Demon Lord stands at the start of boss fight (between the core and forge), the player is warned that their defense "overlaps an enemy spawn area."
|Number of Crystals||Number of Waves||Defense Units||Starting Mana|
|Hazards||Mana Per Round|