You can use either "Mist Body" or "Vylon Tetra" on the same equipped monster to prevent your monster from being destroyed by battle when battling a monster with higher ATK.
Equip this card to "Marshmallon" as it cannot be destroyed by battle, and will destroy the monster it battles. Also, if "The Sanctuary in the Sky" is on the field, you will not take battle damage when it attacks. "Marshmallon Glasses" can be used so that your opponent may not attack other monsters.
After equipping, activate a card that forces your opponent to attack the equipped monster, such as "Battle Mania". This way, all your opponent's monsters will be destroyed. Best in Defense Position to not lose Life Points unless they have Piercing damage.
You can combo this card with "Seven Swords Warrior". Synchro Summon for "Seven Swords Warrior" using "Vylon Stella" as a Synchro Material Monster. You can then activate the effect of "Vylon Stella" to equip it to "Seven Swords Warrior". You can then inflict 800 and destroy a face-up monster on the field.