The obelisk symbolizes male sexuality, power and lofty ideals. It was also a symbol of Ra and was seen as a stabilizing symbol.
The pyramidion (capstone) of the obelisk was meant to reflect the rays of the sun, thereby spreading illumination. Its destruction in the night by unseen power suggests that the illumination that was spread was false. This destruction also highlights the fallibility of human endeavors - man-made objects eventually turn to dust. This is also shown by the crumbling walls and towers of a fortress. Whatever man builds (either physically or metaphorically) will eventually come tumbling down.
Lightning can be seen as a judgment or a punishment. It can also represent a warning of a forthcoming message or situation.
The pyramid is a symbol of ancient wisdom and of that which is solid, stable and long-lasting. It remains untouched by the lightning. The placement of the obelisk in front of the pyramid suggests that new (false) wisdom had supplanted the ancient wisdom of the pyramid and the lightning was a corrective measure.
Two priests of the false religion are seen running for their lives. They head toward the doorway in the crumbling wall. It offers an escape for those who want to accept it. Doorways also represent opportunities, new pathways and a transition to another state, either physical or mental. They can also represent liberation or the entrance to a new life.
The dove can symbolize the passing from one state to another. It can also bear a message (in this case that change needs to occur).
The snake is a symbol of transformation because of its ability to shed its skin. It can represent knowledge and power as well as evil and corruption. Serpents were also seen as guardians of temples and other sacred spaces because they would hold their ground instead of retreating. In this card, the serpent would be protecting the obelisk of false beliefs and therefore would represent the human inclination to hold tight to current beliefs even in the face of evidence that those beliefs are wrong.
The sky suggests either the coming dawn (symbolizing the promise of a new day) or the setting sun (symbolizing a warning of the difficult night to come).