Let's see....we've had a sphere, a pyramid, a disc, and a cube. Not much left that Isis 5 could be.....
Isis Adventure FB page shows a polyhedron. Gonna be expensive to mill, so maybe it's just a placeholder, but the Isis IV image showed a cube before Tessarisis.
On the decoding of the clues, just assume "the" is a very common word (or better yet, look for encrypted "Tessarisis"), and you can pretty much work out the rest of the words from that.