Moses raising the serpent in the desert is mirrored on the right hand side by a crucifixion scene, again in three panels.
We can infer the identity of some of the characters in this scene. The centre panel showing Jesus on the cross would seem to have Mary, Jesus' mother and John who was entrusted by Jesus to care for her.
The right hand panel shows the Roman Centurian and quite likely Joseph of Arimathea, holding a flask. The thief being crucified looks somewhat tortured, possibly representing the one who taunted Jesus.
The left hand panel shows a sad but less tortured thief, possibly having been assured by Jesus of his place in paradise. At the foot of the cross are two women, Mary Magdalene with her jar and probably Mary the Mother of James.