This is a keycap designed to fit MX Cherry switches on most mechanical keyboards. Its original purpose was to allow me to create a macro and assign it to the key it replaced, enabling me to press a single button to launch Destiny 2.

~update~ Please let me know if you find a way around this, but the Battle.NET app needs to be open for the macro to work. Kind of disappointing, but what can you do...
Thanks, guys <3