Preheat oven to 375 degrees. Line 2 baking sheets with parchment paper or silicone mats.
In a large bowl, combine spinach, feta, ricotta, mozzarella, parsley, shallots, eggs, 1/4 teaspoon salt, and 1/8 teaspoon pepper. Stir until well combined.
Spread one sheet phyllo dough on a clean work surface; brush with melted butter. Place another sheet of phyllo on top of the first and brush it with butter. Place a third sheet of phyllo on top of the stack and brush it with butter, too.
Using a chef’s knife or kitchen scissors, carefully cut the phyllo in to thirds. Place 1 tablespoon of the filling on the end of each strip of phyllo.
Starting with the end of the dough strip with the filling, fold one corner of the phyllo over the filling to form a triangle. Continue folding the dough, keeping it in a triangular shape (like folding a flag).
Place on prepared baking sheet and brush with melted butter. Repeat with remaining phyllo dough and filling.
Bake until brown and crisp, about 20 minutes. Let cool at least 10 minutes (filling will be very hot). Serve warm.