Brenn Frostblade, the Runesmith of Frost

Runic Armor (Recharge 5–6): Brenn can conjure an icy armor around an ally within 30 feet, granting them a +5 AC bonus until the start of Brenn’s next turn. If the ally is hit while this armor is active, the attacker takes 10 (3d6) cold damage, and the armor shatters.

Glacial Spear (Recharge 5–6): Brenn conjures a massive ice spear and hurls it at a target within 60 feet. The target must make a DC 16 Dexterity saving throw, taking 30 (6d8) cold damage on a failure, or half as much on a success.

Spellcasting Brenn is a 10th-level spellcaster. His spellcasting ability is Intelligence (spell save DC 16, +8 to hit with spell attacks).

Cantrips: Frostbite, Toll the Dead

1st level (4 slots): Ice Knife, Shield

2nd level (3 slots): Mirror Image, Ray of Enfeeblement

3rd level (3 slots): Counterspell, Animate Dead

4th level (3 slots): Ice Storm, Greater Invisibility

5th level (1 slot): Cone of Cold

Multiattack: Brenn makes two attacks with his Runic Bolt.

Runic Bolt: Ranged Spell Attack: +8 to hit, range 60 ft., one target. Hit: 14 (3d6 + 4) cold damage plus 4 (1d8) necrotic damage.

Ice Shield (Recharge 5–6): When an ally within 10 feet is targeted by an attack, Brenn can create a spectral barrier, granting +5 AC to that ally for the attack. If the attack hits while the barrier is up, the attacker takes 10 (3d6) cold damage as the shield shatters.

Frozen Interference: When Brenn sees a spell being cast within 30 feet, he can disrupt the casting. The caster must succeed on a DC 16 Constitution saving throw or the spell fizzles, consuming the spell slot without taking effect. This reaction recharges on a roll of 5–6 at the start of Brenn’s turn.