Spellendar is a powerfully fooling piece of close-up or parlour scale mentalism that leaves audiences reeling. Using the specially supplied diary (or using one you have written yourself) you have a random date chosen, with a random word. Using a regular deck you have a random card chosen. These are genuine choices, and there is genuinely no way to know what the audience members have chosen.
You deal to the date and card they chose using the specially supplied deck, and there at that date is their chosen card, with their chosen word on the face of it. The effect is self-working, with an incredible finale that is deeply inexplicable.