How can I obtain the Ancient Daedric Style?
You can find the Ancient Daedric Motif chapters via the antiquities system by digging for Antiquities in the Deadlands.
Is it part of the ESO Base game or do I need a DLC or ESO plus subscription?
To be able to obtain the Ancient Daedric Style you need to own the Deadlands DLC or have an active ESO plus subscription.
Additionally you need have unlocked the Antiquities Skill Line which you can learn if you own the Greymoor Chapter.
Greymoor is also part of ESO Plus (since June 2021).
You can unlock and use the Antiquities Skill Line as long as your ESO plus subscription is active.
What do I need to craft the Ancient Daedric Style?
To craft the Ancient Daedric Style you need Pristine Daedric Heart which can be obtained also via the antiquities system.
Have you created Ancient Daedric Style video so I can look how it looks like?
Yes, I have created a youtube video for this topic:
Monday, the 27th of September, 20121
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ESO Crimson Oath Style