Hello,
I've beaten the first two seraphs (the flame girl and Izana), I've also completed both Citadel Spear and Gate of Guidance, but now I have no idea what to do/where to go next...! There are still two doors that I can't open in the Plaza, but I've been searching every dungeon again and it looks like I'm really stuck.
So far I have:
Commander's key
Prison key
Manager's key
Secretary's key
Izana's key
Citadel's key
Cheers to anyone who can unstuck me
