shield

When you activate cheat mode and reveal the map, you can see that AI's units have certain numbers and characters at their states, as opposed to what the human player's units can have ("F", "S", "G", "I", ..). I suspect these are debug infos for the developers that describe what the AI is...

I have shieldimng, access to power and cities bigger than 25, but arcology shielding isn't even in the build menu.