Preheat the oven to 350 F and grease a 9x9 baking dish.

In a bowl, combine the diced mangoes and the blueberries with the sugar, cinnamon, cardamom, allspice, ginger, cloves, and lemon juice. Toss to blend and then add in the cornstarch and mix well.

Transfer the filling mixture to the greased baking dish and set aside.

In a clean bowl, combine the flour, oats, and brown sugar. Stir well to blend. Add the cubed butter and cut it in with a pastry cutter, or crumble it in with your fingers until the mixture is crumbly and the butter is evenly distributed.

Sprinkle the crisp mixture evenly over the fruit filling.

Bake the crisp in the preheated oven for 35 to 40 minutes, or until the topping is golden brown and the filling is bubbling.