EXTRA: Glass Fandango Achievement in Vampire Survivors

You'll first need to obtain the new weapon Glass Fandango, and it can only be obtained on Whiteout. Refer to EXTRA: Whiteout (5G) for unlocking that level.

Load up Whiteout and head north to collect the spear-shaped weapon on your map. This will give you the Glass Fandango weapon. Now simply level up and choose it to level it up to level 7, unlocking this achievement. This will also add the Glass Fandango into the weapon rotation of every character when leveling up.