C# Custom Object Editor Error

Hi, i have this object i created in C# called Skill. this is the object :

 public class Skill {
     string Name;
     float Effect;
     float CastTime;
     SkillType Type;
     float Cost;
     int Times;
     float Range;
     int Thumbnail;
     EffectProperties Ep;
 
     public Skill(string Name, float Effect, float CastTime, SkillType Type, float Cost, int Times, float Range, int Thumbnail, EffectProperties Ep){
         this.Name = Name;
         this.Effect = Effect;
         this.CastTime = CastTime;
         this.Type = Type;
         this.Cost = Cost;
         this.Times = Times;
         this.Range = Range;
         this.Thumbnail = Thumbnail;
         this.Ep = Ep;
     }
 
     public string namE {
         get{ return Name; }
         set{ Name = value; }
     }
 
 public float effect {
     get{ return Effect; }
     set{ Effect = value; }
 }
 
 public float castTime {
     get{ return CastTime; }
     set{ CastTime = value; }
 }
 
 public SkillType type {
     get{ return Type; }
     set{ Type = value; }
 }
 
 public float cost {
     get{ return Cost; }
     set{ Cost = value; }
 }
 
 public int times {
     get{ return Times; }
     set{ Times = value; }
 }
 
 public float range {
     get{ return Range; }
     set{ Range = value; }
 }
 
 public int thumbnail {
     get{ return Thumbnail; }
     set{ Thumbnail = value; }
 }
 
 public EffectProperties ep{
     get{ return Ep; }
     set{ Ep = value; }
 }
 }

 public struct EffectProperties {
 private bool atTarget;
 private bool projectile;
 private int particles;
 private float lifeTime;
 
 public EffectProperties(bool atTar, bool Proj, int Par, float lifeT){
     atTarget = atTar;
     projectile = Proj;
     particles = Par;
     lifeTime = lifeT;
 }
 
 public bool AtTarget{
     get{ return atTarget; }
     set{ atTarget = value; }
 }
 
 public bool Projectile{
     get{ return projectile; }
     set{ projectile = value; }
 }
 
 public int Particles{
     get{ return particles; }
     set{ particles = value; }
 }
 
 public float LifeTime{
     get{ return lifeTime; }
     set{ lifeTime = value; }
 }
 }

 public enum SkillType{
     passive,
     offensive
 }

and i have made an editor script for it so i can see the object in the inspector when ever i type public Skill myVar; int a script. but the problem is that i keep getting an error from the SkillEditor.cs script that says error CS0030: Cannot convert type UnityEngine.Object' to Skill' and i dont know how to solve it. please help, here is my SkillEditor.cs script:

 using UnityEngine;
 using UnityEditor;
 using System.Collections;

 [CustomEditor (typeof(Stats))]
 public class SkillEditor : Editor {
     public override void OnInspectorGUI(){
         Skill pp = (Skill)target;
         GUILayout.Label("Skill Object Editor");
         pp.castTime = EditorGUILayout.FloatField("Cast Time",pp.castTime);
     }    
 }

thanks for reading