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!]
1-3 Star Servants Tier List
Altria Pendragon (Lily)
How to farm EXP cards & level fast
Best Craft Essence: Craft Essence Tier List
Mysterious Heroine X (Alter)
Chocolate Craft Essences
Holy Night Supper
Piece of Year 2030 (A Fragment of 2030)