The āyāt (miraculous signs) granted to the Prophets and the karāmāt (extraordinary graces) bestowed upon the awliyāʾ (friends of Allah) are true.
These signs are firmly established for the Prophets, and the karāmāt are indeed real for the saintly servants. As for the phenomena reported to have occurred—and to occur—for the enemies of Allah, such as Iblīs, Pharaoh, and the Antichrist (al-Dajjāl), we do not call them āyāt or karāmāt. Instead, we refer to them merely as the fulfillment of their needs, for Allah, exalted is He, sometimes grants the requests of His enemies as a way of leading them on and punishing them. They become deluded by these favors, which only increase their arrogance and disbelief. All of this is within the realm of possibility.