This monster is found in front of the Erbe Royal Villa. You can't miss it.
Ohhhman these monsters are tough. It's pretty hard to do physical damage to them, so go all out on your magic. A bunch of them start off somewhat close together, so you can consider opening up with area magic.
They occasionally cast Golden Armour (黃金鎧甲), which raises their STR and DEF. The STR boost is a definite concern. In my gameplay, I find that a "regular" rhino does around ~850-950 damage, but a boosted one can do up to 1500 damage!
Enter the Grancel East Block and go north. Just below the exit to the airport, you can find the Museum on the left side. Enter it and talk to the old man on the right side of the top floor where he shows you a clue card. Stolen artwork and a clue card can only mean Blblanc is at it again...
The first clue is to find "the watcher of time" at an old general's house. Go to Grancel West Block and enter the house beside the church. Head upstairs and investigate his clock.
The next clue is "a symbol on the ground" which is WTF cryptic. Head to Grancel South Block and investigate the statue of the bird.
The last clue is to look for "the gray knight's resolve" in a foreign country's building. Head over to Grancel East Block and enter the Republic of Calvard's embassy at the bottom. Head up one flight of stairs and enter the library on the right side. The middle bookshelf has "The Puppet Knight" volume 15. Read it and there is one final card, to the "hero's ball".
Almost done >_<
Since you're in the embassy already, talk to Ambassador Eresa at the top. Exit and enter the arena and take the right hallway. Save and equip everyone with freeze-resist equipment, then enter the gladiator's pit for a boss fight.
Focus on the boss, then worry about his minions. The boss is weak to fire, so spam fire spells. Probably the only notable thing is that the boss can cast Diamond Dust (鑽石星塵), which is an area spell. This fight should be pretty easy.
After the boss fight, a treasure box will magically appear and the team will magically reappear in the museum.
Unbelievable Paste (不可思議的糊), Salamander Armour (火龍草鎧甲), Silver Gauntlet (白銀護腕)
Revive Capsule, Awakening Medicine
Enter the Grancel Sewers West Block. The monster is aaaaall the way at the end of the sewers, so it's much easier to follow the map than words. But since the map isn't ready yet, I'll try to give directions room-by-room:
The monster is pretty tough, so I encourage you to fight monsters along the way to train up your CP.
Before engaging in battle, give everyone an accessory to protect against Faint. If you only have one Feather Chestpin, give it to Kloe. Also, you should be able to equip Olivier with powerful enough quartz so that he can cast Fire Bolt EX.
Ohhhhgawd is this a tough battle. The trees are able to summon Scissor Crabs (whose attacks can cause faint) and also leech HP when they attack (which almost always guarantees a drawn out fight). And to top it off, their Mud Splatter (泥漿四濺) ability is a small-circle area attack that lowers a stat (either SPD or MOV, which makes sense since it's mud).
A few general ideas of how to plan your strategy for this. Kloe is basically your last resort insurance policy. Don't hesitate to S-Break her when things go horribly wrong (or when the AT meter doesn't give you a chance to catch your breath).
Try to keep the trees together (this can be easier said than done as the battle progresses) so that you can take advantage of Fire Bolt EX's area damage, in addition to any Chain Attacks and Zin/Olivier's S-Crafts.
It goes without saying to steal Critical AT bonuses when possible. Don't forget also that if there is a Critical AT bonus on your turn but nobody has 100+ CP to steal it, you can still do quite a bit of damage with a Chain Attack.
I would suggest allowing Zin to steal the first Critical bonus, as he can do around 1800-2000 damage to each tree. Olivier doesn't do as much damage (~800 or so?), so I would prefer to use his S-Break to clear out the battlefield if the trees summon too many Scissor Crabs.
Red Bug (紅蟲), x200
Crystal Heels (水晶高跟鞋)
Meat with Bone (骨肉相連), Strange Star (詭異之星) [Weapon for Olivier]
Enter the Grancel Sewers East Block. Again, the monster is aaaaall the way at the end of the sewers. And again, I don't have a map ready yet, so here is the room-by-room directions:
You should consider spreading out your team for this one. The Irritable Bubbles' main attack is to cast Plasma Wave (等離子波動), which shoots electricity in a "thick" line for the entire battlefield. So get ready for some hurt if you accidentally "line up" your characters.
This battle should go much easier than the previous sewer monster one. Just stay out of the way of Plasma Wave, and focus your attacks on the armours first.
As a side note, the High Performance Armours are able to summon more Irritable Bubbles and the bubbles will self destruct when killed (just like all the others), so make sure you have enough HP before dealing that last hit.
Exit Grancel to the south and go right (towards Erbe Royal Villa). In the next map, take the bottom fork in the road.
Pretty standard monster fight. One thing to be aware of is that the Giant Flaming Eagles can summon more Hellfire Sparrows. Wouldn't be a bad idea to kill them off first (use Water arts to make it easier).
Do note the Giant Flaming Eagles have an attack that can cause Faint. Would be a wise idea to equip anti-faint accessories beforehand.