Let's start by breaking down the characteristics of Mythic Rares as offered to us by Mark Rosewater in 2008
It is worth noting that if the spell doesn't resolve, gifts will not be received
Cecil, Dark Knight [Foil] #91 (Magic Final Fantasy | Magic Cards) prices are based on the historic sales

Historic Agent of Treachery Ajani, Nacatl Pariah Ancient Tomb Arid Mesa Armageddon Blood Moon Bloodstained Mire Brainstorm Broadside Bombardiers Channel Chrome Mox Commandeer Crop Rotation Dark Depths Dark Ritual Daze Demonic Tutor Devoted Druid Eldrazi Temple Entomb Field of the Dead Fireblast Flare of Cultivation Flare of Denial Flare of Duplication Flare of Fortitude Flare of Malice Flooded Strand Food Chain Force of Will Frantic Search Fury Grief Harbinger of the Seas Intruder Alarm Land Tax Library of Alexandria Lightning Bolt Mana Drain Marsh Flats Memory Lapse Mishra's Bauble Misty Rainforest Mox Opal Mystical Tutor Natural Order Necropotence Nexus of Fate Oko, Thief of Crowns Once Upon a Time Painter's Servant Polluted Delta Preordain Pyrokinesis Ragavan, Nimble Pilferer Reanimate Scalding Tarn Scholar of the Lost Trove Seething Song Show and Tell Sneak Attack Solitude Spreading Seas Strip Mine Subtlety Swords to Plowshares Temporal Manipulation Thassa's Oracle Tibalt's Trickery Time Warp Uro, Titan of Nature's Wrath Vampiric Tutor Veil of Summer Verdant Catacombs Wilderness Reclamation Windswept Heath Winter Moon Wooded Foothills Many cards banned in Pioneer are also banned in Arena's Historic format, though some, like Winota, Joiner of Forces, are notably absent from Historic's ban list due to the format having a wider range of responses for it

With interesting abilities, striking artwork, and only 250 copies in existence, its no wonder that this chase rare from Murders at Karlov Manor tops out as the most valuable card in the set
Chaos: Whenever you roll Chaos, each player exiles the top card of their library