Borivik Windheim

Bolts of undead slaying Borivik has a half-dozen bolts of undead slaying. If he strikes an undead with one of these bolts, it must make a DC 17 Constitution saving throw, taking an extra 6d10 piercing damage on a failed save, or half as much extra damage on a successful one.

Magic Resistance. Cornelius Watson has advantage on saving throws against spells and other magical effects. 

Spellcasting Cornelius Watson is an 18th-level spellcaster. His spellcasting ability is Intelligence (spell save DC 17, +9 to hit with spell attacks). Cornelius Watson has the following wizard spells prepared:

Cantrips (at will): fire bolt, light, [Tooltip Not Found], shocking grasp

1st level (4 slots): detect magic*, identify, mage armor,
magic missile

2nd level (3 slots): detect thoughts, locate object*,
mirror image, misty step

3rd level (3 slots): clairvoyance*, counterspell, fireball

4th level (3 slots): arcane eye*, banishment

5th level (3 slots): rary’s telepathic bond*, scrying*,
wall of force

6th level (1 slot): true seeing*
7th level (1 slot): teleport
8th level (1 slot): mind blank
9th level (1 slot): foresight*
* Divination spell of 1st level or higher.
Portent. (Recharges after Cornelius Watson Casts a Divination Spell of 1st Level or Higher.) When Cornelius Watson or a creature he can see makes an attack roll, a saving throw, or an ability check, Cornelius Watson can roll a d20 and choose to use this roll in place of the attack roll, saving throw, or ability check.

Multiattack. Borivik makes two melee or ranged attacks. or cast one spell

Spell attacks.  +9

Shortsword. Melee Weapon Weapon Attack:+9, Range 5 ft, one target Hit: 8 (1d6+5) Piercing damage

Heavy Crossbow. Ranged Weapon Attack: +9 to hit, range 100/400 ft., one target. Hit: 6 (1d10 + 5) piercing damage.