Events are a great alternative source of Blood Flaked Bone, since Rare Catalysts can often be exchanged for event currency or obtained as clear rewards. And finally, the Guild Member Shop and the Guild Aid system also allow you to farm lots of Rare Catalysts in general, which include Blood Flaked Bones.
Source #1: Adventure Mode – Unrecorded History 8-9 Drifting Tomb (Best Source)
Stage 8-9 of the Unrecorded History (Prologue) Chapter is the best place to farm Blood-Flaked Bone. This is because this particular stage drops Blood Flaked Bone and has the Rare Catalyst featured in its AP Exchange Shop. Blood Flaked Bone costs 120 AP each to purchase, and you can only buy up to 10 of them per week. If you want to farm more AP, I recommend bringing along Pets with AP acquisition rate-boosting skills on your farming runs.
Source #2: Events
Each event features a variety of farmable Epic and Rare Catalysts in the Event Currency Exchange Shop, which might just include Blood Flaked Bone. You can also obtain Rare or Random Catalyst Chests as rewards from story events, check-in events, or giveaway events. Always keep an eye out for Events, as they’re sure to come with all sorts of farmable Catalysts and resources.
Source #3: Guild Member Shop
You can buy a Random Catalyst Chest in the Guild Member Shop for 180 Brave Crests and a Random Rare Catalyst Chest for 30 Commander’s Armbands. The weekly purchase limit for Random Catalyst Chests and Random Rare Catalyst Chests is three per week and five per week, respectively. You can easily buy both of these chests just by playing the game regularly every week and participating in guild activities.
Source #4: Guild Aid
The Guild Aid system allows you to request crafting materials, awakening materials, and Catalysts from your guildmates. You can only request aid once per day, and you cannot refresh the request until the day after you’ve made it in case it wasn’t fulfilled. If you plan on requesting Catalysts from the Guild Aid often, make sure you’re paying it forward by donating excess Catalysts yourself, as they are quite hard to farm. Nobody likes a leech!