The Leviathan Shield in Blox Fruits is an equipment that can be crafted at the Beast Hunter NPC. Once equipped, its user will be granted protection against all kinds of damage.

The Rotten Ring in Jujutsu Infinite is an accessory that can be worn to gain seriously offensive buffs. For players who constantly engage in PvE or PvP battles, this ring can do wonders.

They will provide you with enough Curse Spins and Koins so that you can upgrade your hero faster than anyone else. However, you should use them ASAP!