Going to toss my hand here. Again, I'm not intimate with Farland so I may be doing things that go against the grain of the fluff. Just looking at the classes and converting those.
I look at everything about you. Who you are, where you've been and where you'll be.
Prerequisites: Elf or half-elf, ranger or rogue
The Shadowalker is a defender of Elven lands, skilled in scouting, reconnaissance, and defense. Shadowalkers are a brotherhood of twilight and shadow, ranging abroad in secret service to the Elven homeland. The Shadowalkers account for much of the military and societal information the elves have about the outside world, and they are often the first, and sometimes last, line of Elven defense.
Shadow Armor Action (11th level): When you spend an action point to take an extra action, you can make a stealth check. You gain a bonus to AC and Reflex equal to the result of the stealth check divided by 5.
Speak with Animals (11th Level): You can speak with any animal of natural, fey or shadow origin with an Intelligence score of at least 3.
Shadow Walk (16th Level): If you have concealment, cover, superior cover or total concealment at the start of your turn, you can shift up to your speed as a move action. You can move through enemy's squares during this movement and must end your move with concealment, cover, superior cover or total concealment against at least one enemy.
Shadow Shank Shadowwalker Attack 11
From the darkness, a shining blade reaches out. And in the same instant, it disappears.
Encounter | Martial, Weapon
Standard Action Melee or Ranged Weapon
Target: One creature that you are hidden from
Attack: Strength vs AC (melee) or Dexterity vs AC (ranged)
Hit: 2[W] + Strength modifier damage (melee) or 2[W] + Dexterity modifier damage (ranged) and you can make a stealth check to remain hidden and avoid being noticed.
Miss: You can make a stealth check to remain hidden and avoid being noticed.
Shadow Jump Shadowwalker Utility 12
You walk through the shadows like a dark veil.
Daily | Martial
Requirement: You must have concealment, cover, superior cover or total concealment from at least one enemy.
Effect: You can teleport up to 10 squares. You must end your movement with concealment, cover, superior cover or total concealment from at least one enemy. You become hidden to any enemies who you had concealment, cover, superior cover or total concealment from at the start of the move and still have concealment, cover, superior cover or total concealment from at the end.
Liason's Knife Shadowwalker Attack 20
You take a moment to study your foe before striking. Afterwards, you know their weaknesses.
Daily | Martial, Weapon
Standard Action Melee Weapon
Target: One creature
Attack: Strength vs AC (melee)
Special: Before you attack, you can make a knowledge check, using the skill relevant to and lowest DC to the creature. If you succeed, you gain combat advantage for this attack.
Hit: 4[W] + Strength modifier damage.
Special: If you succeeded on the knowledge check, the creature gains vulnerability 5 to all your attacks for the remainder of the encounter.
Miss: Half damage and no vulnerability.
Kind of winged it, but still tried to incorporate ideas from the existing PrC as well as some ideas of my own. I don't know if the power names were taken or not. Feel free to correct my wording or anything like that.