I have successfully located the party searching for th eyes, at least some of them. The goddess did warn that the party would be incomplete, but I did not understand her words until now. Thanatos contains the usual and expected dangers, and this group seems capable of dealing with the environment.
Our most recent battle involved agents of Orcus who exclaimed of an alliance with Vecna. Though not unheard of, it was unexpected. I will report more as information is obtained. I have faith Ioun did not speak of this for a reason. Either it is of no consequence, or will be dealt with easily.