In a cocktail shaker, combine the reposado tequila and lime juice. Add ice and shake vigorously until the mixture is well-chilled.

Pour the crème de cassis into the bottom of a highball glass, creating the base layer.

Using the back of a spoon, carefully pour the tequila and lime juice mixture over the crème de cassis, aiming to preserve the distinct layers.

Fill the glass with chilled ginger beer, pouring gently to maintain the layered effect.

Open a charcoal capsule and sprinkle half of its contents over the top of the drink. Gently stir the charcoal into the surface of the cocktail, creating a mesmerizing black layer.

Garnish with one or more brandied cherries and add a festive straw for an elegant touch. Serve immediately and enjoy your visually stunning Black Diablo.