He is Yunalescaīs father isnīt it?
So how can he looks like that?
That squid is in fact another summon of Yu Yevon(like the pagodas).
A summoner doesnīt necessarily live inside the summon(this idea has no basis).I know that Sin can be used as a shield but wasnīt it smarter if a sosia of Yu is inside making people think that after so much sacrifice to go through the shell they manage to defeat Yu?This is called psychological manipulation.Maybe he wanders somewhere on Spira laughing on people.