Only a few brave travelers (mostly dead) know the truth about the Warrior Queen of Skifander, and the live one known isn't talking about her much.
She is alleged to be a strong Spark, and is likely a fairly absolute ruler over her hidden city. Though her exact relation to Zeetha, Daughter of Chump, is not revealed in the comic, the novelizations confirm that she is Zeetha's mother.[1] This queen dispatched her kinswoman to the outside world "to see what the rest of the world was getting up to." [2] Considering her appellation and the emphasis Zeetha has placed on battle training, she may be the best fighter of her people as well. Unique to the Skifandrian women is the color of their hair, which being green may have saved Zeetha from being murdered out of hand by the pirates who captured her while she was sick (thinking it exotic) ✣ Zantabraxus is shown with dark green hair, which may be artistic convention or perhaps a regal trait.
Klaus
When Klaus first meets Zeetha and has an animated exchange with her in the Skiff tongue[3], his last word is "Zanta--!" just before he is cut off by the Spark-infecting slaver wasp, leading attentive fans to the (very reasonable) conclusion that he was about to invoke the name of the Skifander Queen (see below). It has been essentially confirmed by the Foglios (though not in-strip) that "Chump" is a/the name used by Klaus while he was in Skifander. This, combined with the information from the novel[1], makes it almost certain that he and Zantabraxis are husband and wife.
Zantabraxis in the novelization
Zantabraxis is the mother of Zeetha according to Agatha H. and the Voice of the Castle.
Her formal relationship with Chump is unknown but, as with his wife[4], he hasn't seen Zantabraxis in years.
Zantabraxus in The Works
Zantabraxus from the card game The Works
One card in The Works card game is identical (or very nearly so) to the Queen pictured in the description of Zeetha's adventure: Zantabraxus, who has the labels Queen and Spark.