Spellcasting. The Eternal Guardian is an 8th-level spellcaster. Its spellcasting ability is Charisma (spell save DC 16, +8 to hit with spell attacks). It has the following sorcerer spells prepared:  

• Cantrips (at will): Mage Hand, Prestidigitation, Minor Illusion
• 1st level (4 slots): Shield, Magic Missile, Detect Magic
• 2nd level (3 slots): Mirror Image, Misty Step
• 3rd level (3 slots): Counterspell, Dispel Magic, Slow
• 4th level (2 slots): Banishment, Arcane Eye

Arcane Ward. The Eternal Guardian has an invisible magical barrier around it. Whenever it takes damage, the ward takes the damage instead. If the ward is reduced to 0 hit points, the Eternal Guardian takes any remaining damage. The ward has 50 hit points and regains all its hit points at the start of each of the Arcane Guardian's turns.   Arcane Knowledge. The Eternal Guardian has advantage on Intelligence (Arcana) checks and can cast spells from scrolls as if it were a wizard of level 10.   Magic Resistance. The Eternal Guardian has advantage on saving throws against spells and other magical effects.