The Guardian is a 10th-level spellcaster. Its spellcasting ability is Charisma (spell save DC 18, +8 to hit with spell attacks). The Guardian has the following spells prepared.   1st level (4 slots): bless*, command, compelled duel   2nd level (3 slots): aid*, lesser restoration, zone of truth   3rd level (2 slots): daylight, dispel magic, spirit guardians   * The Guardian casts these spells on itself before combat.

Arcane Siphon (recharge 5-6). Once per turn, after landing a melee weapon attack against a creature, the Guardian can choose to forgo any damage that would be dealt to that creature. Instead, they must succeed on a DC 18 Constitution saving throw or lose a spell slot of the highest level they have available. The Guardian gains 1d8 1d8 temporary hit points per spell slot level that was siphoned in this way. If the creature has no spell slots left to siphon, it instead loses attunement to a random one of its attuned magic items.   Duelling. When the Guardian is wielding a melee weapon in one hand and no other weapons, it gains a +2 bonus to damage rolls with that weapon.   Divine Healing. The Guardian regains 10 hit points at the start of its turn.   Divine Smite (4 charges). When the Guardian hits a creature with a melee weapon attack, it can expend a charge to deal 2d8 2d8 radiant damage to the target, in addition to the weapon's damage. This damage increases by 1d8 1d8 if the target is an undead or fiend.   Immutable Form. The Guardian is immune to any spell or effect that would alter its form.   Magic Resistance. The Guardian has advantage on saving throws against spells and other magical effects.   Legendary Resistance (3/day). If the Guardian fails a saving throw, it can choose to succeed instead.   Structurally Vulnerable. After sustaining enough damage, the Guardian will begin to break down and lose access to some of its systems as parts of it are destroyed. When the Guardian is reduced to 50 hit points below its hit point maximum, the creature that dealt the last portion of that damage can choose to destroy a part of the Guardian, resulting in a negative effect (refer to the table below). Players do not learn the effect of any particular system until they have destroyed it.   SYSTEM - EFFECT
GENERATOR - Destroying the magic siphoning generator on the Guardian's back removes the Arcane Siphon feature.
HOLY AVENGER - Destroying the Holy Avenger removes the Divine Smite feature.
HOLY SYMBOL - Damaging the Holy Symbol on the Guardian's chest removes the Divine Healing feature.
LEGS - Damaging the Guardian's legs reduces movement speed by 10 feet.
SHIELD - Destroying the shield results in a -2 penalty to AC.