I just ran this deck through YGOPro and the chains you can produce are insane lol
I would still love to read your explanations for everything though. I've only just got back into the game, I've never played with synchros, tuners, Xyz, etc.
Last time I played was probably about 8-9 years ago so I'm super rusty.
The aim of the deck is to use Dark Magical Circle to control the field. Magician Navigation and Eternal Soul can trigger it at will, and Navigation also protects Circle and Soul from being destroyed using its second effect. A good opening is to summon Rod to find Circle, or one of the two Traps if you already have it, then pass the turn and when your opponent tries something, summon Dark Magician and banish it. Then, in your next turn, you can summon a second Dark Magician off Eternal Soul if you have it, make Ebon Illusion Magician, and banish for days.
Gonna quickly go over the things that aren't so obvious:
Kycoo/Night's End: DARK Spellcasters for Magician Navigation, if the opponent is playing a deck that uses their graveyard or banishing. Night's End is also a Tuner so I can make Synchro monsters.
Pot of Duality: I mostly Special Summon on my opponent's turn, so it's a fairly safe inclusion. There's a few cards I want to find ASAP, and Pot of Duality helps with that.
Book of Moon: A fairly versatile Quick-Play spell that interrupts my opponent's plays and lets me summon Magician of Dark Illusion.
Breakthrough Skill: Similar to the above - interrupts monster effects and gives me two chances to summon Magician of Dark Illusion.
Champion's Vigilance/Solemn Warning: Sometimes I want spend a card to just say NO. As they're Counter Traps I can't chain Magician of Dark Illusion, and the condition/cost can be awkward, but they're useful to have in case I can't deal with something another way.
Vanity's Emptiness: Most decks rely on Special Summoning. If I can get a Dark Magician or two and banish anything bigger, it makes it hard for the opponent to come back. Magician Navigation protects it from effects that would remove it.
Eradicator Epidemic Virus: Hey, this deck summons 2500 ATK DARK monsters!
Most of the Xyz monsters are just generic good Rank 7s. Azure-Eyes protects itself and summons back a Dark Magician next turn, Stardust protects Eternal Soul, Scarlight is neat because it doesn't kill Dark Magicians, and Catastor is generally useful.
You have no ways of summoning Dark Magician on your turn (without first setting a trap card). Why is this not a problem, why no Dark Magic Veil, or Chocolate Magician Girl?
That's a good point. I hadn't really thought of that when building the deck. I want to play the deck mostly reactively, hence the high Trap count - I'm fine not doing much in my own turn if I can stop the opponent doing much in theirs. I also want most of my Special Summoning to be done in my opponent's turn so I can use Pot of Duality effectively. I suppose being able to summon Dark Magician during my turn would be useful when going second, so I can banish something with Circle immediately.
The problem is that there aren't any searchable ways to summon Dark Magician on the first turn - I don't think I could reliably get Dark Magic Veil when needed, and Chocolate Magician Girl doesn't summon Dark Magician during my turn anyway.
That said, I want to drop an Illusion Magic (I really don't need two copies with Apprentice Illusion Magician around), so I could try Dark Magic Veil there.