Relics
Relics are class locked items and are a progressive item you should be upgrading as you venture deeper into the game universe.
Relic level 1 to level 3 can be upgraded on the shop
Relic upgrade level 4 can be found by killing titans and Asgardian captains in Act 4
Relic level 5 can be found in the Castle in Act 4
Relic level 6 can be found in the World 2 bosses Archn, Myth, and the Demon Commander in Act 1 and 2
Relic level 7 can be found in the World 2 bosses God Devourer, Stitcher, and the Horror Smith in Act 2
Relic level 8 can be found in the World 2 bosses Gaia, Apocalypse, and Bahamut in Act 3
Relic level 9 can be found in the World 2 bosses in Asgard in Act 4
Relic level 10 can be found in the World 2 bosses in the Castle In Act 4
Relic Key can be crafted in World 3 by acquiring boss items in the following areas.
Aspect Soul
Raguel (Purge, 1-5)
Hero's Honor
Divine Honor (Fields of Glory, 2-1)
Soul Dematerializer
Divine Light (Soul Shifter, 2-2)
Life Container
Grinder (Forge of Souls, 2-3)
Strange Fog
Eternal Guide (Infinite Gateway, 2-4)
Strong Armor Scrap
Rage (Transporter, 2-5)
Shard of Destruction
Divine Destroyer (Transporter, 2-5)
Magic Arrowhead
Shadow (Transporter, 2-5)
Vibrating Blades
Edge (Transporter, 2-5)
Death Bomb
Guidance (Transporter, 2-5)
After Acquiring all the keys on the transporter area you will gain access to the top of the world tree where you can find the last piece
Powerful Seraph Soul
Imperial (Boss of World Tree, Before Maker)
Class Relic Key is different from the Maker key which can only be acquired by the Maker Class