In the Blizzard Interface Source Code for Dragonflight Patch 10.1, there are new warnings implemented for Hardcore realm selection, which was first noticed by Twitter User Meorawr and tweeted by Solanya. Hardcore is a Classic Era community driven game mode, where players delete their characters upon death.
Early last year the Hardcore community hosted a Road to Ragnaros event, where 40 hardcore players dove into Molten Core and killed Ragnaros!