Sicariss was a smoothsnake that served Korvus Skurr as his advisor; she also perched on top of the head of the Doomwyte leader as his crown. She was the descendant of Sumiss. Korvus often used Sicariss to hypnotize his minions so he could know whether or not they were lying to him. Since the raven leader was very superstitious, she would pretend to communicate with the catfish Welzz (who Skurr believed was an oracle) and then tell Skurr what to do from her own judgment.
Skurr made a pact with the adder Baliss the Slayer, saying if he succeeded in bringing fear to Redwall, he would give all the reptiles in his domain for him to eat. Upon hearing this, Sicariss made plans of her own; from that point on, she no longer trusted Skurr and instead avoided him. Later, Skurr tossed her to Welzz when he discovered that she had been routinely lying to him.