1. Boss Fights
2.1. Monster Bane (Ereshkigal Boss Fight)
2.2. Desert Dragonslayer (Aeronite Boss Fight)
2.3. A Legend from Times Past (Bhunivelze Boss Fight)

2. Miscellaneous
2.1. Globetrotter – Proof of rebuilding all bridges

Monster Bane
Proof of mastering all creation and conquering even the Ultimate Lair.
Ereshkigal is the final boss of the Ultimate Lair in Lightning Returns: Final Fantasy XIII.

This boss is completely optional and missable! To get to the Ultimate Lair you have to beat all main story quests and complete a certain amount of side quests. Basically, you need 100 side quests points: 1-star missions are worth 2 points, 2-star missions are worth 4 points, 3-star missions are worth 8 points. So if you do around 30-40 quests of different difficulties, you should be good to go. The Ultimate Lair will then unlock on Day 13. Fight through all of its 33 levels and defeat as many Last Ones as possible along the way. They drop extremely strong equipment which will come in handy for this fight.

Now as far as the boss fight goes: Poison & Overclock are the key for a quick victory.
1. Use Magic attacks until Ereshkigal is staggered
2. Cast Deshell, Slow, Imperil, Poison
3. Keep spamming overclock, use Elixir or Ether when you run out of EP.

If you are going for all trophies / achievements, then you would probably have the Elixir at this point of the game (earned by selling 100 soul seeds to merchants). It will completely refill all of your EP, which guarantees a quick victory. There’s also an Ether on floor 32 of the Ultimate Lair. So if you don’t have an Elixir, at least get the Ether (restores 3 EP) and you’ll be fine.

This video was captured on the first playthrough! However, this boss fight is significantly easier in New Game+.

Desert Dragonslayer
Proof of victory over the dragon Aeronite who brought terror to the Dead Dunes.
Aeronite will start spawning from day 7 onwards. He travels through the Dead Dunes area and changes locations every couple of hours. The video shows his location from 16:00 – 20:00.
It is highly recommended to wait until the second playthrough before doing this. If you are going for all trophies or achievements, then you will have to do a second playthrough anyway. In New Game+ you can massively upgrade your weapons and shields, which will easily give you an extra +2000 attack/magic.

It is important that your EP are all filled up before starting this fight. Bring as many recovery items as possible. Preferrably Phoenix Wings, Ethers and a Potion that grants bravery (such as the “Warrior’s Potion” which can be acquired from merchants).

Here’s a basic breakdown of the fight:
1. Use magic to stagger Aeronite. You’ll have to stagger him 4 times before achieving a knockout. Only then he can be seriously wounded.
2. Once Aeronite is knocked out, immediately use a potion that grants bravery (=more attack power).
3. Cast deprotect (lowers the enemy’s physical defence).
4. Spam Overclock & your strongest physical attacks. You should use a level 4 heavy slash with the “Soldier of Peace” garb equipped. This should deal anywhere from 100,000 – 500,000 damage per hit. This garb is obtained by completing a side quest in Jagd Village.

A Legend from Times Past
Proof of the true savior, who overthrew even the god of light to lead the people to a new world.
This trophy is obtained by beating the final story boss.

Before going into this fight, you should definitely get the Ultima weapon. It can be obtained in the very last room before the boss fight. You have to complete four trials to unlock it. This special weapon grants +2500 attack & +2500 magic. Bring as many recovery items as you can carry.
The boss fight consists of four stages. Bhunivelze will completely refill all of his HP in each stage. Make use of your overclock ability as often as possible and cast Deshell & Imperil to make your magic attacks more powerful. In the last stage his attacks become significantly more powerful, so save your overclock for this point and unleash your strongest magic attacks to stagger him quickly.

Globetrotter
Proof of building strong bridges to span the depths between continents, making all the world one.
To unlock this trophy or achievement, you have to complete all 3 “Roadworks” quests from the Canvas of Prayers. These quests become available on day 9. You can still complete them on the following days.
Each quest requires you to find 2 key items. Once you have everything, return to the Canvas of Prayers. This will open up the bridges that connect all areas, which allows you to go everywhere by foot. You can also find some strong monsters on these bridges and there are lots of Chaos Spheres for farming Soul Seeds (useful for “Seed Collector” and “Unearthly Apothecary”).