This is the first definitive suspicion that I've actually got from Achmea. Before, his goals and method were strange but very clearly defined. He wants him and his people put to rest. It genuinely did seem like the Caringorm business was coincidence and he did just fall in love with her (I guess "her" is correct at this point). At least my scepticism wasn't as bad as the other people here.
However, if that were the case, why would he keep her arm for 102 years? Especially when all the lunarians are eager to grind them up. It finally makes me feel that he does have some sort of sinister plan or at least a different method to achieving his goal than we thought. Admittedly, we do see that he still had a couple of fragments of Antarcticite when Phos showed up but even then it wasn't much.