The CW has released an official description for the next-to-last episode of Arrow Season 3.
The episode is called “This Is Your Sword” and here is the write-up with new spoilers:
AL SAH-HIM TAKES HIS FINAL STEPS TO ASCENSION; ROY AND THEA REUNITE — Oliver/Al Sah-him (Stephen Amell) finishes his training and is left with two final tasks to become the next Ra’s al Ghul. Ra’s (guest star Matt Nable) threatens Nyssa (guest star Katrina Law) and delivers some shocking news. Meanwhile, Malcolm (John Barrowman) makes a surprising offer to Team Arrow and Thea (Willa Holland) goes to see Roy (Colton Haynes). Wendey Stanzler directed the episode with story by Erik Oleson and teleplay by Ben Sokolowski & Brian Ford Sullivan (#322). Original airdate 5/6/2015.