Cold Iron: Cold Iron weapons count as magic for purposes of overcoming Sidhe Nobles damage resistance.  Any character carrying a significant quantity of iron has advantage on Savings Throws made against the Magic and Special Abilities of the Sidhe.  This includes but isn't limited to iron armor and shields for example.

Magic Weapons. The Sidhe Noble's weapon attacks are considered magical

Spellcasting. The abjurer is a 13th-level spellcaster. Its spellcasting ability is Charisma(spell save DC 16, +8 to hit with spell attacks). The Sidhe Noble has the following spells prepared:

Cantrips (at will): Druidcraft, Friends, Minor Illusion, and either Fire Bolt or Ray of Frost for Summer and Winter courts respectively.

1st level (4 slots): Charm Person, Faerie Fire, Silent Image, and Hellish Rebuke dealing Fire damage for the Summer court of Cold Damage for the Winter Court.

2nd level (3 slots): Enthrall, Misty Step, and Suggestion, 

3rd level (3 slots): Bestow Curse, Counterspell, and Dispel Magic

4th level (3 slots): Charm Monster and Greater Invisibility

5th level (2 slots): Geas and Cone of Cold or Fireball for Summer and Winter courts respectively.

6th level (1 slot): Programmed Illusion and Investiture of Flame or Investiture of Ice for Summer and Winter courts respectively.

Glamour: The Sidhe can cast Alter Self at will so that they might carry out their machinations and amusements in most environments without drawing excessive attention.  They are vain creatures however, and often leave some small but noticeable faerie trait like unusual eye, fingernail,  or hair color 

Veil:  The Sidhe are adept at concealing magic allowing them to turn invisible until they attack or cast a spell, or until their concentration ends (as if concentrating on a spell). While invisible , they leaves no physical evidence of her passage, so they can be tracked only by magic. Any equipment they wear or carry is invisible  with them.