Manadeep was supposedly built at the beginning of time, but this is just the interpretation of the forest folk. Its ruins are quite old, however, used by Arka's avatar to travel between Rym and the boreal sphere, and as a conflux for earth elementals. Its strange architecture and magnificent stonework are a testament to the nature of its divine builders, now long dead. Their remains lie scattered among the crumbling white ruins, among fallen ranks of mechanized infantry now cloaked in moss. The battle that destroyed the archaic city ended with the invasion of Lith by countless swarms of mechanical warriors, and the death of Arka's core.
Near the heart of the sunken ruins rests an immense step pyramid, rising from a pool of dark water. Huge stone goliaths lurk in the gloom, surrounding the half-sumberged structure in a perfect circle. They hold aloft a huge ring of stone, the inner surface of which is lined with clusters of luminous green crystal in the same manner as a geode. Its outer surface is covered in a rich carpet of moss, though white stone faces show through in even spacings all around the circumference. The ring actually floats just above the mossy stone goliaths, rotating very slowly in mid-air. Every so often, a thin arc of green electricity will jump between crystals within the ring, suggesting that it may still be active. The cap stone of the pyramid rises into the center of the ring, and is carved with intricate glyphs of planar travel and cosmic calendars.
Anyone standing on the capstone when the gateway opens experiences a bombardment of green energy arcs as the ring begins to spin, faster and faster, weaving a portal of crackling green light. The portal transports everything on the pyramid's summit to a similar structure within the forest sphere of Lith, in a similar ruined city. Activating the portal is no small feat, however, and few have braved the great forest depths simply to try. The process involves powerful nature magic that no mortal remembers, ad to make matters worse, the artifact itself has grown fragile and delapitated. Nobody can tell for certain if it will withstand another cycle, though the results of being caught in a failed transit would no doubt be disastrous.