User blog comment:B214/Volume 23 discussion blog/@comment-77.188.219.183-20170424155339/@comment-29963364-20170425131329

In Issei's original [DxD] (the one he used against Rizevim and Apophis), Ophis "blessed" Issei to awaken Ddraig's full power, and the "infinity" power within Issei's body. She basically did what Old Kai did for Gohan in the Buu Saga of Dragon Ball Z.

Now for the pseudo [DxD] (that Issei currently uses), Ophis "rigged" the form so that the "infinity" power within Issei wouldn't awaken, because his body can't handle the strain yet (it would be like Izuku Midoriya using [One for All] in Boko no Hero].

So the two forms are...

* Pseudo [DxD] = Ddraig's full power awakened by Ophis' blessing.


 * "True/Original" [DxD] = Ddraig's full power + Issei's "infinity" power.