Cave mage

Magic Resistance. The Cave mage has advantage on saving throws against spells and other magical effects.

Spellcasting. The Cave mage is an 10th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 17, +9 to hit with spell attacks). It has the following spells prepared:

Cantrips: acid splash, minor illusion, light, mage hand, ray of frost

1st level (4 slots): color spray, detect magic, [Tooltip Not Found], fog cloud

2nd level (3 slots): shatter, blindness/deafness, misty step

3rd level (3 slots): lightning bolt, counterspell, fear

4th level (3 slots): ice storm, fire shield, phantasmal killer

5th level (2 slots): cone of cold, dominate person

Psychic onslaught.  the Cave mage may use its action and expend a spell slot to gain a number of additional reactions, equal to one plus the level of the expended spell slot. These additional reactions can only be spent on the psycic assault ability.

Psychic assault. if any creature within 40 ft. of the Cave mage attempts to take a bonus action, action, reaction or move, theCave mage may spend its reaction to try to briefly control the mind of that creature. The creature must then suceed on a DC 16 wisdom saving throw, or the Cave mage chooses how the creature uses that action/reaction/bonus action/move. (The Cave mage cannot select a different action than the one attempted)