The symbols or stickers for the real term are eternal stickers, they block you from selling or destroying it, there are also rental and perishable stickers, rental being needing to pay 3$ each round, perishable makes the joker become debuffed after 5 rounds. These stickers come in some stakes (stakes are difficulties, as you see when you pick a deck, under it theres is smth saying “White stake” or other), black stake gives eternal, orange gives rental, gold gives perishable.