Metaphor: ReFantazio

When you get freedom to properly explore Port Brilehaven on 07/23 (which is when the Infiltrate the Charadrius operation will commence), you’ll have access to - among other things - the Varmareno Coliseum on the Arenafront Wharf.The Varmareno Coliseum is available both day and night (except on days with bad weather) and you can get involved in 2 aspects:

• Ranked League
• Gauntlet

The Gauntlet is what you need for this achievement, but in order to access the Gold Class battles in the Gauntlet you need to advance through the Bronze leagues to the Gold leagues in Ranked League battles (there are 3 levels in each). Unfortunately you can only do 1 at a time.

That said, the rewards are pretty decent so it’s worth seeing it through anyway. They are as follows.

• Bronze III - Man O’War Gloves (Blue) (Strength & Magic +3, Prevents Paralysis)
• Bronze II - Blessed Water x 10 . Graced Water x 5 / Heavenly Water x 2
• Bronze I - Fortune’s Grasp (Blue) (Receive 1.5% Archetype experience & Luck +10) + Rainbow Bathblossom (Protag +2 to all stats, including Max HP and MP)
• Silver III - Miracle Igniter (Purple) (Revival Skill)
• Silver II - Hero’s Jewelled Root x 5
• Silver I - (Need 2 Brawlers for this fight) - Full Moon Medal (Legendary) (Large MP recovery every turn in battle) + Chain of Bonds (Blue) (Eases conditions on skills that require multiple members of the same Archetype)
• Gold III - Jade Jian (Purple) (Can be Purified - 365 dagger)
• Gold II - Hero’s Jewelled Root x 10
• Gold I - Gamblers’ Manual (Legendary) (Doubles Critical Hit damage) + Overlord’s Sash (Purple) (Increases power and MP cost of MP Synthesis skills) 

Now, once you’ve done that you can take on the Gold Class Gauntlet challenge, which is basically wave after wave of random enemies who are for the most part easy - unless you get Moldilich, who’s perhaps the hardest of the lot and reflects most spells. 

For this I’d take the main protagonist in with the Prince Archetype with 3 Heavy elemental spells (Ice, Fire and Lightning), an MP regen ability and also equip an MP regen weapon/piece of armour too (as well as some back up MP potions, just in case).

Then, it’s a matter of targeting the weaknesses of random dungeon enemies and getting through 30 waves. I did this at level 73 (after beating the Dragon Trials) so I was incredibly overleveled and breezed through it in no time. I basically spammed Royal Slash and Radiance, as there are a lot of enemies with Light weaknesses in the Gold Class Gauntlet. I even did it solo as well, as I forgot to add my party back together after doing one of the solo Ranked League challenges, so you shouldn’t have a problem with it.

Once you beat wave 30 - which is the end - the ‘Coliseum Champion’ achievement will unlock. Don’t worry, it won’t take you long. We did it in about 10-15 minutes. 

If you’re struggling, come back when you’ve levelled up some more - and have more mastered Archetypes (for the permanent stats boosts).