[Build Advice] One of the PCs is secretly a powerful archfey

[Seneschal]

My group has been entertaining the idea of returning to a GURPS campaign we had played half a decade ago - a horror/mystery campaign set in a dark fantasy world. For the previous campaign, GURPS worked wonderfully; the characters (built on 150 pts) were riddled with tragic flaws and hidden regrets that slowly consumed them as the world around them descended into darkness - something that GURPS portrays fairly well mechanically.

This time, a player with no prior GURPS experience approached me with a character concept the way they'd do it for D&D5e - "I wanna be an elf bard," complete with a drawing they made of a dashing pointy-eared scoundrel. Now, elves had not been part of the previous campaign, and the concept was a step too swashbuckly for the tone of the campaign, so we ruminated a bit on how to include them when I had an idea: instead of a mundane human, the character could be a unique fey entity - an enchanting, immortal trickster that plays cruel games with people. "Elf bard" on steroids.

To be honest, I was apprehensive of how a 150-pt GURPS character would feel for someone who comes from a 5e background. The other players know fairly well what to expect, but the transition tends to be jarring for newcomers, especially if their high-fantasy concept can't quite be realized on a limited point budget. So, I figured I might as well pull them behind the GM screen and hammer out something special the way only GURPS allows.

Thankfully, the player knew exactly what I was hinting at (warning, TV Tropes link, don't lose your afternoon), and they were on board. Now, I just need some help putting the archfey together; it's been a while since any of us touched GURPS.

The specific fae archetype we're going for is something like the Gentleman with Thistledown Hair from Jonathan Strange and Mr. Norrell:

• outwardly humanoid - no tiny body or wings;
• immortal (time-wise) and hard to perish (pointy-thing-wise);
• charming, foppish and playful, at least at first glance;
• offputting and creepy at a second glance;
• implacable alien mindset;
• a heartfelt yet fleeting fascination with mortals;
• deceitful and manipulative, although incapable of lying directly;
• constrained by laws which they only respect the letter of;
• powers of enchantment, illusion and travel between worlds, but generally has to bargain, coerce or persuade the consent of mortals before affecting them;
• a limited ability to manipulate reality, or just access to untold treasures and ancient lore, enough to "grant wishes" of sorts.

What I'm looking for is how to put the above onto a character sheet, which Advantages and Disadvantages to use, the best fit for a magic system, whether there are some sourcebooks or Pyramids that could help me, etc. I'm also curious about more fae lore that I could use to flesh them out and maybe give them weaknesses and limitations.

The point total is not an issue, although I'd prefer to be as conservative as possible (under 500 if possible); the character is a kind of "monster PC" with which the player and I will subtly nudge the plot around, but I would still like them to be able to engage with the other characters on the same scale.

Thanks in advance.