Trying to spawn a Prefab after 50 seconds - it works kind of.

Here is my current code. Forgive me if the post formatting is wrong, it the first time I am posting. the Prefab spawns after 50 seconds, however I get this Error. Also the prefab does not play its animation when it spawns. I am 100% a beginner scripter. Thank you for any help!

UnassignedReferenceException: The variable Boss of BossSpawn has not been assigned.
You probably need to assign the Boss variable of the BossSpawn script in the inspector.
UnityEngine.Object.Internal_InstantiateSingle (UnityEngine.Object data, Vector3 pos, Quaternion rot)

 using UnityEngine;
    using System.Collections;
    
    public class BossSpawn : MonoBehaviour
    {
        public GameObject Boss;
        GameObject bossClone;
    
        void Start ()
        {
            StartCoroutine(WaitSpawner());
        }
    
        IEnumerator WaitSpawner()
        {
            yield return new WaitForSeconds(50f);
            Debug.Log("it has been 50sec");
            bossClone = Instantiate(Boss, transform.position, Quaternion.identity) as GameObject;
        }    
    
    	void Update () {
    	
    	}
    }

Have you actually dragged the game object into the game object field, in the inspector with the script in.
you said the prefab had spawned so i assume you have, if so your null reference may be from another object you attached the script to, and didn’t assign the prefab.
As for the animation, that has to do with the default animation state, open up the character controller and make sure the animation you want playing is set to default