“For the rest of the game, you can’t play spells.”
Well that’s an interesting line of text! This is what the epic keyword entails, so why are you working so hard to fire off your 7-mana Epic spell if you can’t actually cast anything else?
Enduring Ideal allows you to search your library for an enchantment and put it directly onto the battlefield. You can’t cast spells for the rest of the game, so your draw step is actually a detriment (since you could draw the enchantment you want to search it out from your library), but you can get the most powerful option left in your deck every single turn during your upkeep. Resolving an Enduring Ideal should end the game, but it requires enough acceleration to cast while it’s still relevant, and you need to have enough powerful enchantments in your deck to make sure you actually win the game when it resolves.
Your mana acceleration starts with Lotus Bloom. If you hit your land drops, you can get right up to 7 mana by suspending the Lotus turn 1 and then just hard casting your Enduring Ideal. You also have Simian Spirit Guide for some extra mana in the middle stages, although you’re likely going to use it earlier to get some lock pieces into play.
This is a nearly mono-white deck, and you have lots of white enchantments you can cast early to build up a huge number of white mana symbols for your devotion count. This means that you can play 4 copies of Nykthos, Shrine to Nyx and use that to accelerate out a quick epic spell. You can actually get some enchantments into play early, use those to ramp a couple more enchantments into play, and now your Nykthos will be making 7 mana on its own.
Form of the Dragon is your win condition. This is one of the most flavorful spells ever printed—it effectively turns you into a firebreathing Dragon. Your life total becomes 5, and it resets each turn, just as if you had 5 toughness that needed to be extinguished to win the game. It also completely shuts down ground creatures from attacking you, and it hits for 5 each turn. As a Dragon, you can attack players or creatures, keeping big flyers from killing you while eventually finishing your opponent off.
There are plenty of spells that can with your enchantments, not to mention all of the combo decks that might be able to totally ignore something like Form of the Dragon. Dovescape can shut down any spells from being effectively cast by your opponent as they’re all getting countered. For the creatures with key abilities such as Kiki-Jiki, Mirror Breaker or Qasali Pridemage, you have Overwhelming Splendor to search out and shut them down.
The majority of decks in Modern look to win the game through combat damage. Ghostly Prison is a great lock piece to keep creatures from being able to come after you and it only costs 3 to get into play. Sphere of Safety gives you another, more powerful form of Ghostly Prison for a bit more mana that can make sure the Dovescape tokens or potential swarms can’t get near you.
You also have Phyrexian Unlife to effectively gain a bunch of life early and to combo with Form of the Dragon. If they want to attack you for a million damage, Unlife will put you at negative life, but you won’t pick up any poison from the attack. Form of the Dragon will send you right back to 5 life and make them do it again.
Leyline of Sanctity can negate burn spells, discard spells, and it’s a free way to get a WW enchantment onto the battlefield turn 0 for Nykthos. Runed Halo can shut down a number of threats and adds a ton of devotion early on. Suppression Field can shut down many combos and entire mana bases as fetchlands can no longer be sacrificed for free, and trying to use Kiki-Jiki, or just about any ability in the Affinity deck, becomes a nightmare.
The red splash is for Blood Moon to help slow your opponent down and potentially lock them out of spells on turn 2 or 3 with Spirit Guide. It will also turn off Nykthos, but if they’re not casting anything, it’s all good!
Enduring Ideal is such a sweet deck that uses a bunch of rarely played enchantments to keep you alive before using 7+ mana enchantments to finish off your opponent. If that sounds enticing to you, then definitely check this one out!