5th Singularity E Pluribus Unum: Des Moines (Surveillance Fortress) free quest is the best AP & time-saving location to farm Claw of Chaos. You'll get about 2x Claw of Chaos by spending 180AP.
7th Singularity Babylonia: Ur (Jaguar Park) free quest is one of the other locations to farm Claw of Chaos. You can also get Seed of Yggdrasil.
2nd Singularity Septem: Germania (The Dark Forest) is the first location you unlock to farm Claw of Chaos, but the item rarely drops.
You can also farm Claw of Chaos at Wednesday Daily Quest: Berserker Traning Ground. For other item drops, check the table below.
Rashoumon event (Ibaraki Douji event)
Murder at the Kogetsukan
Inheritance of Glory
5 Star Servants Tier List: Best Servants [5/9 updated!]
FGO Reroll Tier List [5/11 updated!]
Best Servants [★4]: 4 Star Tier List
How to farm Pieces & Monuments
Best Craft Essence: Craft Essence Tier List
Phoenix Plume (Phoenix Feather)
Mecha Eli-Chan & Mecha Eli-Chan Mk II
Berserker of Eldorado (Penthesilea)
Jeanne d’Arc (Alter)
Caster of Nightless Castle
Mana Compass (Mana Gauge)
GUDAGUDA Poster Girl
Gem Magecraft: Antumbra