the chest is aldy open when i revisited that place
i'm in the midst of collecting items for weapon/armor so sometimes revisited 3-4 times
wow how come u got many 5* char

you can start the 2 knight event first instead of 1000 ark as the 2 knight dungeon is also the easiest one. hard mode only level 33 and very hard in lv 40 only.

you can do in this route, do 2 knight ---> IDA part 1 ---> 1000 Ark ----- IDA part II. then if free want to play some content can start fishing and mining.
just completed IDA part II 4 episode but havent gotten all the reward. try my luck on Claude banner as i wanted him coz i lack wind units and clause is consider good wind piecing unit. and gotten below 5*. although no claude but i am happy with what i get. Roll on 5 30pm if you wanted to be superstitious.