'Arrow': Nyssa al Ghul Returns in "The Thanatos Guild" Preview

The CW has released a new promo for "The Thanatos Guild", the upcoming sixteenth episode of Arrow's sixth season.

The episode will see the return of fan-favorite Nyssa al Ghul (Katrina Law), who hasn't been seen in the series since last season's "Lian Yu" season finale.

As the promo shows, Nyssa will be returning to warn Thea (Willa Holland) about a new threat - a rogue group of League of Assassins members. While that challenge might not sound as daunting on paper, it will apparently have a massive effect on the topography of Arrow.

"In an unforgettable episode that will change Arrow forever, Katrina Law returns as the Daughter of the Demon, Nyssa Al Ghul," executive producers Wendy Mericle and Marc Guggenheim explained earlier this year. "Nyssa comes to Star City to warn of an impending danger that will threaten everything we know and love."

"The Thanatos Guild" will be the follow-up to tonight's episode, "Doppelganger", which sees Roy Harper (Colton Haynes) returning to the fold as well. While fans will have to wait three weeks to see this episode, tonight's cliffhanger shows that it will be well worth the wait.

You can view the official synopsis for "The Thanatos Guild" below:

NYSSA AL GHUL COMES BACK TO STAR CITY WITH A DANGEROUS MESSAGE FOR THEA — Nyssa Al Ghul (guest star Katrina Law) returns to Star City to warn Thea (Willa Holland) that a group of renegade League of Assassins members are planning to attack her.

This group, led by Athena (guest star Kyra Zagorsky), is intent on finding a mysterious box that Malcolm left behind and will stop at nothing to get it. Nyssa helps Oliver (Stephen Amell) come to a life-changing realization.

Joel Novoa directed the episode written by Beth Schwartz & Ben Sokolowski (#616)

Arrow airs Thursdays at 9/8c on The CW. "The Thanatos Guild" will air on March 29th.