Arianna Ortega, the Red King, and the Lords of Outer Night chose Chichén Itzá for enacting a ritual sacrifice for a Bloodline Curse using Margaret Angelica Dresden, the youngest in her family and aimed at Harry Dresden, Susan Rodriguez and any others in their family such as Thomas Raith and Ebenezar McCoy. The Red Court stashed their goodies near ley line confluences; Chichén Itzá is a really big confluence. The Red King identifies it as his Country Seat.