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

Spellcasting. The archmage is an 18th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 17, +9 to hit with spell attacks). The archmage can cast disguise self and invisibility at will and has the following wizard spells prepared:

Cantrips (at will): fire bolt, light, mage hand, prestidigitation, shocking grasp

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

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

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

4th level (3 slots): banishment, fire shield, stoneskin*

5th level (3 slots): cone of cold, scrying, wall of force

6th level (1 slot): globe of invulnerability

7th level (1 slot): teleport

8th level (1 slot): mind blank*

9th level (1 slot): time stop

*The Wyrdfell casts these spells on itself before combat.

 Dragon Command.  The Wyrdfell can take control of its dragon, forcing it to take any  action in its stat block

Dragon Connection. the Life Force of the Wyrdfell isconnected to that of its dragon. If either of them dies, so does the other.

Longsword. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 10 (1d8+6) slashing damage, or 12 (1d10 + 6) slashing damage if used with two hands.