Equestrian Princess Luna - Beast/XYZ-4/Dark/Effect  
Summon Requirement: 2 Level 4 “Equestrian” monsters  
Effect: Cannot be Tributed and cannot be destroyed by battle once per turn. If this card is XYZ Summoned: draw 1 card. Once per turn (Quick Effect): you can detach 1 XYZ material from this card, then target 1 face-down Spell/Trap card you control: Send that card to the GY and replace this cards’ effect in the current chain with that card. Once per End Phase; If this card is sent to the GY: Special Summon 1 “Equestrian Princess Celestia” from your GY. (This is not considered a Synchro Summon. This is not in the text but it’s just to clarify.)
 
You can play this card freely on Duelingbook. I’ll even upload a few decklists that I’ve made just to get a basic feel of how the cards work. You’ll be able to change them to your liking.
 
Copyright for MLP:FIM belongs to Hasbro and Lauren Faust.  
Copyright of Yugioh belongs to Konami and Kazuki Takahashi.