You just know that it’s important.
What is Castle Heart Decay in V Rising?
Your Castle Heart in V Rising is the most important part of your home.

However, just like you, your Castle Heart needs blood to survive.
If a Castle Heart isn’t supplied with enough Blood Essence, it will start to decay.
As you place Blood Essence into the Castle Heart, you’ll see the timer below the grid increase.

If you allow a Castle Heart to run out of Blood Essence, it will start to decay.
Castle decay is a slow process.
Castle Durability is the protection your walls and structures have against enemy attacks.

That’s all there is to the simple matter of preventing Castle Heart Decay in V Rising.
If you get into combat on the road, check that you knowhow to heal in V Rising.