Item description:

go through the secret caves (use shortcut) and massacre the boss. use the item he gives you to battle another boss. do PA in central city to trigger a harder final boss version.
gabrie celests, iselia queen and limiter off final boss

you shouldnt have trouble with these bosses since i'm pretty much maxed... but in case you do then create algol shield and give it to chisato to one shot them (little chance). also remember to switch rena's strategy to "use anything" so she can be offensive with her support skills.