Defense Buildings are necessary to secure your own base. You can only upgrade them with gold. There are different kind of Defense building, some use magic others the power of your unit. Furthermore there are traps and mines you can use.
|Ballista||Watchtower||City Wall||Divine Hand|
|Anti-Arcane Cannon||Prophet Tower||Obscurity Tower||Ragnarok|
|Gnomic Mine||Spike Trap||Hades Trap||Darkfire Mine|