The White Knight is a minor character on Once Upon a Time. He guards two red doors, one of which leads to Wonderland's Well of Wonders. The Knight is only able to answer "yes" or "no" questions, and when he does answer, he must lie.
After the Curse
The White Knight serves as an obstacle for Alice and Cyrus. ("Dirty Little Secrets")
In search of Wonderland's Well of Wonders, Alice and Cyrus come across two red doors, guarded by a White Knight, who seemingly automatically exclaims, "Two doors appear along a stony path and travelers always wonder which door will lead them to the Well, and which will drag them under. Choose poorly and meet certain doom, there is no room for blunder." This confuses the couple at first, but Alice soon realizes that once the Knight can only answer "yes" or "no," it is also a lie. Alice proceeds to ask if one door leads to the Well, and once receiving her answer, she chooses the opposite, thus opening it up. The couple is excited to have succeeded, but once crossing though, Cyrus tells his true love that this is something he must do alone, so he asks her to wait, which she agrees to. ("Dirty Little Secrets")
The White Knight continues guarding the door. ("And They Lived...")
Cyrus is continuing to lead Amara through the woods with a flaming torch, and she comments that his Alice is quite brave. He asks if it's because she's leading an army, but she says that it's because she talked back to her future mother-in-law, causing Cyrus to grow amused and tell his mother that his fiancée speaks her mind. This Amara can gather, and she says that she approves. Cyrus is happy to hear this, and it isn't long before they arrive at the entrance to the Well of Wonders: two red doors, guarded by a White Knight. Cyrus conceives that they're close, and he and his mother begin approaching, the former knowing which door is the correct one to pass through. ("And They Lived...")