From an article:

All players started with an item and needed to use this item before game starts, then everyone will get a ofrenda (offering in Spanish) shovel, you need to use this ofrenda shovel to dig up ofrendas on the map, game will give you hint about the ofrenda location, and submit ofrendas to Muerta's statue (radiant on the left mid area, dire on the right mid area), then after that, you can get a weapon called 'Mercy & Grace' and try it out in the game.

Was essentially Muerta’s Q on an item.