Chancellor of the Annex

Magic Dampening Aura. Chancellor of the Annex has an aura that extends out 150 feet. Any spells cast by its enemies in this aura must succeed a WIS saving throw with a DC of 15 or the spell will fail upon being cast, using up a spell slot with no effect. 

Spellcasting. Chancellor of the Annex is a 9th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 15, +2 to hit with spell attacks). Chancellor of the Annex has following spells prepared:

Cantrips (at will): acid splash, poison splash

1st level (4 slots): magic missile, unseen servant

2nd level (3 slots): cloud of daggers, web

3rd level (3 slots): stinking cloud

4th level (3 slots): Evard's black tentacles, stoneskin

5th level (2 slots): cloudkill, conjure elemental

Multiattack. Chancellor of the Annex makes two attacks with its claws. Chancellor of the Annex then casts a spell.

Claws. Melee Weapon Attack: +5 to hit, reach 5 ft., 1 target. Hit: 9 (2d6 + 2) slashing damage. The target also takes 1d4 poison damage. After a successful hit, the target must make a CON saving throw with a DC of 10. Nothing happens on a successful save. On a failed save, the target becomes diseased with ichor. A diseased target gains 1 level of exhaustion after every long rest. After a long rest, the target may roll a CON saving throw with a DC of 15. On a success, the target is no longer diseased. On a fail, the target remains diseased. If the target is unable to overcome the ichor disease before it dies, it will revive in an hour's time after death as a Contagious Nim.

Counterspell. Chancellor of the Annex can cast Counterspell as a reaction. This is an innate ability and does not cost Chancellor of the Annex any spell slots.