Several mechanics express whats happening in the story currently, says Fleischer
Like most Magic: The Gathering cards, the value of Ring of Xathrid depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Magic 2013)
Scout Unit Hakbal of the Surging Soul Holy Avenger Horizon of Progress Howlpack Piper Hunting Grounds Ilharg, the Raze-Boar Illusionary Mask Incandescent Soulstoke Insidious Fungus Introductions Are in Order Jhoira, Ageless Innovator Joint Exploration Journey to the Oracle Kaalia of the Vast Kami of Bamboo Groves Kellan, the Kid Kinscaer Sentry
The latter lets the player cast a W12
That's only the beginning of what it does though, as it has three other potential uses: If you have two copies (or Evolution Witness), then you can loop these effects to avoid decking