Here it is, a bit easier than expected.
No Spoilers Guide: Don’t play defensively. =)

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Here it is, a bit easier than expected.
No Spoilers Guide: Don’t play defensively. =)
Brave Frontier: Trial X4 - Gazia Pre-Guide
Video Guide will be out tomorrow.
Here is a quick rundown of the mechanics of the fight and the best trick to beating him.
Phase One: From 100%-0% HP.
Turn One: Summons Random (Fire, Earth, Lightning SBS Vortex Mob) (NO DAMAGE REFLECT for first Summon)
Thresholds: 50% HP - Light Suppression (Stealth for 2 Turns) Followed by Extermination. 50% Mitigation is fine.
Nothing too scary until Phase 2, however it seems he can randomly use Ruination during this phase? Weird... I had it happen once.
Phase 2:
Will remove your buffs on 2nd or 3rd turn. The next turn he will cast Annihilation. Make sure you get mitigation back up before this. Any time he removes your buffs during the fight, a nuke is coming the next turn.
Sometimes around 60-55% HP or so (Near the end of the dragons tail on the boss HP bar) he will use a surprise ruination. Only had this happen once out of 3 times.
At 50% he will debuff on turn 1 and then nuke on turn 2 again. Re-buff.
At 40% HP He will enter Stealth. After 2 turns he will come out of it and use Extermination.
After this he drains bb Gauge a lot more and it will become hard to maintain bb spam if you are using the wrong squad.
!!!!! At a really odd % (like 20-17%) he will use Ruination. This may be wrong and it may be after 10 turns. I am just not quite sure.
At around 15-12% HP Left he will use Holocaust. !!!!!
This is the tricky part of the fight. Your best bet is to use a HUGE UBB to push him from 21%+ down PAST his Holocaust threshold. This will allow you to SKIP the Ruination threshold, which is the dangerous one anyways.
After experimenting with a few teams I settled on this squad to one-team it (With a Rhoa friend):
I started off using Grah/Tridon but it’s just not necessary. Better to go with a team that can generate the gauge you need.
Moveset:
Celestial Rising - Big AoE, Removes BB Gauge partially.
Light Suppression - 2 turn Stealth
Call to Serve - Random Unit Summon
Call to Exile - Big AoE upon death of Summoned Unit
Talon of Pain - Medium 3-5k DoT (Bring a Regen Unit)
Dispersal Field - 3 Turn 50% Mitigation
Annihilation/Obliteration - Massive AoE - Not Fixed can be Mitigated and easily dealt with by using ATK Down, 50% Mitigation and 140% DEF buff.
Extermination - Upon exiting stealth mode (Big AoE) Mitigate 50%.
Ruination - 110% Unit HPFixed Debuffing AoE. Guard, however UBB 75% Mitigation weirdly worked for me. Post-patch I think only occurs now at 20% HP.
Mind Wreck - Single target LS Removal (occurs frequently after 15% HP in phase 2)
Holocaust - Massive AoE occurs @ 15% HP in phase 2. 75% UBB Mitigation allows you to survive. WILL NOT kill units (stops dmg at 1 hp).
Again, will have a video guide up tomorrow. Good luck guys!
Global maintenance at 00:00 PST 8th October 2015. It seems Gazia Trial X4 is delayed much longer from announcement date in Japan Tokyo Game Show where it was noted to release in End September 2015.
Nevertheless good content to look forward to given current lull. I wonder what is happening with the Global Chain Chronicles Collaboration, and when.
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Level Up Campaign [Lv. 201-250]
Trial X4: Gazia (will be released at a later date/time)