Pendant

He designed an artifact that was attuned to his eyes. Though small enough to be worn as a sparkling pendant, the artifact could send a signal between-worlds.

"Come back frequently," he'd told Xantcha when he hung the jewel around her neck. "If they've returned, hide yourself far, far away from here, then break the crystal and I will return for my- for our-vengeance. Above all, once you've seen a Phyrexian, stay away from the forest until I come for you. Don't let your curiosity lead you into foolishness. If they find you, they will reclaim you, and you will betray me. You wouldn't want that to happen."

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Planeswalker, Chapter 10