You can access the Sky Pirate's Den via your trust Clan Primer. It's a virtual trophy cabinet where your achievements in Ivalice are acknowledged with figurines depicting character or creatures from the game. There are 30 to collect in all. Each one appears after a specific requirement has been met and grants you a specific title.

Take note that it is possible to unlock some of these (Penelo, Balthier, Fran, Basch and Mountblanc) while you play as Reks at the beginning of the game but it will take a long time and as there is no reward for doing so there is little point in doing that.

FIGURINE TABLE

Figurine	Title	Requirement
Vaan	Master Thief	Steal successfully over 50 times
Ashe	Exemplar	Raise the party's average above level 50
Penelo	Plunderer	Acquire more than 100,000 Gil
Balthier	Assualt Striker	Use the Attack command more than 300 times
Fran	Spellsinger	Cast Magicks over 200 times
Basch	Blood Dancer	Defeat 500 enemies or more
Vayne	Premier Prestidigitator	Use Technicks over 100 times
Reks	Record Breaker	Receive 500,000 Clan Points or more
Rasler	Conqueror	One character must learn all Licenses
Vossler	Jack-of-All-Traders	Obtain all Technicks (you do not have to learn the Licences for all of them)
Gabranth	Mist Walker	Trigger all Concurrences during Quickenings *1
Ba'Gamnan	Scrivener	Complete the Bestiary (you don't have to unlock the second page of information for each monster)
Montblanc	The Unrelenting	Complete a Battle Chain of 50 foes
Gurdy	Spendthrift	Spend more than 1,000,000 Gil
Migelo	Privateer	Sell over 1000 pieces of Loot
Old Dalan	Cartographer	Complete every map (excluding the Bahamut)
Chocobo	Wayfarer	Take more than 50,000 steps
Mimic	Collector	Purchase the Morbid Urn at the Bazaar (it will turn into a Canopic Jar)
Crystal	Runeweaver	Obtain all Magicks (you don't have to unlock the Licenses for all of them)
Deathgaze	Eagle Eye	Defeat the Mark Deathgaze
Fafnir	Wymslayer	Defeat the Mark Fafnir
Trickster	Sharpshooter	Defeat the Mark Trickster
Carrot	Freshmaker	Defeat the Mark Carrot
Gilgamesh	Master Swordsman	Defeat the Mark Gilgamesh
Behemoth King	Lord of the Kings	Defeat the Mark Behemoth King
Hell Wyrm	Radiant Saviour	Defeat the Mark Hell Wyrm
Yiazmat	Hunter Extraordinaire	Defeat the Mark Yiazmat
Ultima	Fell Angel	Defeat the Esper Ultima
Zodiark	Zodiac Knight	Defeat the Esper Zodiark
Belias	High Summoner	Defeat all Espers

*1 This may require a fair amount of practive to achieve. If you find it difficult during the course of the main adventure, choose a Save Crystal close to a ready source of enemies as a base, then return to replinsh your party's MP as required.