Here is the full list of all 50 Ragna Maya achievements.
Clear the Prologue.
Defeated an Arachguhl.
Emptied a Treasure Chest.
Emptied 10 Treasure Chests.
Emptied 20 Treasure Chests.
Emptied 30 Treasure Chests.
Viewed a Memoriam Recording.
Viewed 5 Memoriam Recordings.
Viewed 10 Memoriam Recordings.
Encountered a Witchspawn.
Defeated a Witchspawn.
Fought a Variant Encounter.
Fought a Gateway Encounter.
Defeated an Akasha beyond your level.
Used a Sun Oryx.
Used a Rune Oryx.
Materialized an Ability Tome.
Materialized 5 Ability Tomes.
Materialized 10 Ability Tomes.
Materialized 20 Ability Tomes.
Materialized 30 Ability Tomes.
Defeated a Golonakh Ogre.
Defeated a Hastur.
Defeated a Nightgaunt.
Defeated a Wounded Dragon.
Defeated Olfana.
Defeated Olfana....?
Crystallised a Mirage.
Crystallised a Mirage 3 times.
Crystallised a Mirage 6 times.
Crystallised a Mirage 10 times.
Crystallised a Mirage 20 times.
Crystallised a Hastur.
Crystallised a Nightgaunt.
Crystallised a Lloigar.
Clear Floor 1.
Clear Floor 2.
Clear Floor 3.
Clear Floor 4.
Clear Floor 5.
Clear Floor 6.
Witness the Dullahan's Petrification.
Use a Tier 5 Spear in Battle.
Use a Tier 5 Sword in Battle.
Use a Tier 5 Elemental Greatsword in Battle.
Use a Tier 5 Greatsword in Battle.
Use a Tier 5 Katana in Battle.
Use a Tier 5 Orb in Battle.
Use a Guardian Essence in Battle. (Equipped on Slot 1)
Use a Tier 5 Essence in Battle. (Equipped on Slot 1)