The Cervine Keepsake is a hidden amulet in Remnant 2's The Forgotten Kingdom DLC. Finding it requires some effort, and you'll have to complete other Yaesha-related worlds and tasks.
Remnant 2 How to Get CERVINE KEEPSAKE Amulet (Secret Doe Statue Room) | The Forgotten Kingdom DLC
The Cervine Keepsake refers to the Protector of the Grove, the mighty deer that protects many in the Yaesha jungle. The Cervine Keepsake is a specific one that you can unlock, and it’s a tricky one to find. We’ll explain where to find it in Remnant 2, and what you’ll need to bring with you.
The Cervine Keepsake is received by finding a Protector of the Grove statue while exploring the Deserted Atelier or the Luminous Vale. It can appear in these locations throughout Remnant 2's The Forgotten Kingdom. The statue should resemble a large stag, and is also where you can find one of the DLC's many new rings, the Token of Fortune, if you haven't already picked it up during your travels. Like the Fragrant Thorn amulet, this statue can be a bit tricky to track down, as worlds require rerolling each time you play through Remnant 2.
To get the secret passage to unlock the statue, you must make sure you are wearing the Red Doe Sigil. You can receive this Amulet by going to the Red Throne world of Yaesha and finding the Ornate Lockbox. Be careful not to open it or peek inside, and return it to The Eternal Empress. The court will be surprised that you have discovered such a relic and reward you with the Red Doe Sigil for not opening it.