Stakes of Marika in Elden Ring are a temporary respawn point in the form of a Statues. You will first need to interact with one of these statues; they are generally found near important landmarks or boss locations. After interacting with one, if you happen to die nearby to one, you'll have an option to respawn there. After respawning there, once leaving the area, you will not have the opportunity to respawn there again if you die again.
List of all Stakes of Marika in Elden Ring
There are more than a few of these Stakes; as mentioned above, they will be in valuable places and only need you to interact with it to unlock it as a temporary respawn point. These can be useful for when you die to a tough boss and would rather not walk back from your Site of Grace. Below, you will find all the locations of all the known Stakes of Marika in Eldin Ring.