The Fire tiara is a head slot item used in Runecrafting. This item can be created by using a tiara on the fire rune altar while a fire talisman is in your inventory . Doing this grants 35 Runecrafting experience.
The purpose of the fire tiara is to let you enter the fire rune altar with a left click and since it can be equipped, it frees up an inventory space that the fire talisman would normally occupy.
The Fire tiara counts as a warm item at Wintertodt.