Can I tell a camera to NOT render a certain part of the scene?

Hi,

imagine a vampire game. The vampire can’t see himself in the mirror.

I have two cameras, one is the player camera, the other camera is placed in the level as a “mirror” (Texture2d Render Target).

Now I want the player to NOT see himself in the mirror. So easiest way would be to use a location based opacity material and material instances. The location would be the player and the materials of the player model would be of these instances.
BUT: player looks down and he is now also invisible.

So both cameras, the mirror and the player, do not see the player.

How can I tell the mirror camera to “ignore” the player model during rendering, but the player camera does render it?

Thanks!