This is the list of all Vyrn weapons obtainable in the game at the moment. Once you unlocked one of these, you will received the "What Am I?" achievement as well. More will be added once the DLC characters are released soon.
List of All Vyrn Weapons Skins
These weapons are originally obtainable on GBF through promotional codes that came with their Grand Blues! comic strip that is only available on Amazon JP and Bookwalker JP. In this game, you can unlock these weapons in a few easy steps.
Gran - Vyrn Star Sword
Obtainable by doing 100% damage cut 3 times. This requires both characters to use a Phalanx support skill.
Katalina - Vyrngleis
Equip any other Vyrn weapon in your grid and then beat Katalina's stage on RPG mode.
Charlotta - Claíomh Sovyrn
Listen to the full dialogue while entering the shop menu ten times.
Lancelot - Paravyrnium
Use any Panacea skill at full health, 3 times.
Ferry - Aura Vyrnwhip
Game over 5 times in RPG mode.
Lowain - Vyrn Switchblade
Beat Yggdrasil solo, as Lowain. Win with your own Yggdrasil summon.
Ladiva - Vyrn's Mercy Mask
Taunt 3 times as Ladiva.
Percival - Flamvyrge
Sell any 4 SSR weapons. Easy way is to just buy them from the shop and sell them.
Metera - Vymbul
Skip cut scenes manually 20 times.
Zeta - Vyrionac
Beat Proto Bahamut as Zeta 3 times.
Vaseraga - Bravyry
Finish 5 missions without a partner or support skills equipped. Missions before unlocking the support skills doesn't count.
Beelzebub - Chavyos Matter
Finish the final boss on RPG with Beelzebub or as your partner.
Narmaya - Vyxaba
Pause the game for 60 seconds straight during RPG mode.