Vesuvius

You invoke the essence of magma, transforming into a creature made of rock, magma, and lava. For the duration, you gain the following benefits:

• Your AC increases by 4;
• Your size increases by one category;
• You gain 200 temporary hit points;
• All your melee attacks deal an additional 6d8 incinerating damage;
• You gain immunity to all nonmagical and magical physical damage, and to nonmagical elemental damage;
• You gain resistance to all magical elemental damage;
• You gain vulnerability to glacial damage;

In addition, you lose 10 feet of movement speed and can cast the 3rd-level spell erebus without spending mana, as if cast as a 5th-level spell.