Darkness of Light

See here the midrash where Rav Yehuda and Rav Nechemia argue if the חושך that made up מכת חושך was from a place of great spirituality, or from gehennim.  What is the debate about?  There are two kinds of darkness, there is a darkness where there is no light, there is a lack of any spiritual light.  However, there is another type of darkness, there isn't a lack of light, rather the light is too great to be seen (we discussed this idea here.)  The Tannaim are arguing what light struck the Egyptians, were they opened up to the darkness of their deeds, the darkness of gehennim or possibly Hashem shone upon them a great light that was beyond their capability to see.

The Abarbenel makes an interesting point which he uses to explain why the makkos in our parsha go together and are different from the previous seven.  "And the second reason is that the plague of locusts, the plague of darkness, and the plague of the killing of the firstborn all come from the air; and all darkness the earth.  By the plague of locusts, it states, "And the locusts went up over all the land of Egypt, and rested in all the borders of Egypt; very grievous were they; before them there were no such locusts as they, neither after them shall be such.  For they covered the face of the whole earth, so that the land was darkened."  By the plague of darkness, it states, "And there was darkness over all the land of Egypt."  By the plague of the first-born, it states, "It was in the middle of the night" – "He placed them in darkness, like the eternally dead (paraphrasing Eikha 3:6)."  For this reason, the Torah grouped the last three parashiyot together in a separate parasha." [From here, see his explanation for the significance of the darkness.]

Based upon the midrash we can understand that the darkness is a heightened level of גלוי אלוקות.  The last plagues were the greatest healing for Klal Yisroel, they were electric shocks of 

גלוי אלוקות.  The darkness wasn't a darkness of a lack of light, it was a light which was too great to be handled by the Egptians.  That's why the Abarbenel finds it important to point out the darkness in the final three plagues for it reflects the greatest light.