well... each construction starts with a rotating pentagram. on further progress... claws (like the birth of the undead) will rotate. when nearly done, a the claws go down, the pentegram is upside-down and the building rises quickly. this is info #1
by the way, thanks.
{EDIT 1}
the void temple looks like the temple barracks... but with creepier appearance, large. when upgrading, just add what you would like. at the final upgrade, there should be 5 dark towers (like the ends of the star). Info #2: HQ appearance
{EDIT 2}
the demon barracks looks like a hellgate. 2 sacrificial pits (the whirlpool is violet) is at the end of the hellgate. Info #3: Demon Barracks
{EDIT 3}
Purgatory Lumbermills are like human lumbermills, but with dreadful appearances. Info #4: Purgatory Lumbermill
{EDIT 4}
The steel forge is like a workshop, vut with dreadful appearance. A graveyard will be at the right side, connecting it to the workshop. Info #5: steel forge
{EDIT 5}
Dark Altars are like temple of the damned, but combine it with the altar of darkness. It floats, lava is under (like necropolis). Info #6: Dark Altar
{EDIT 6}
I kinda want to rename it as death altar
{EDIT 7}
The dominus tower is a ziggurat and at the center of the 3 claws is the shrine (the undead campaign skull shapped with fire). The crusader tower is like the dominus tower, but with a dreadful appearance. Info #7: defense towers
{EDIT 8}
pit of death is like the boneyard but with more dreadful appearance. A small, dreadful appearance of a necropolis is at the center, floating. Info #8: Pit of death
{EDIT 9}
Witch rider's nest and the unholy archive is up to you. its your imagination that i cannot describe. im already out. >=(. also if you are good at art, create icons for them pls.
