By means of a secret Mantra or formula a spiritual guru or God when pleased can donate or transfer spiritual energy to others... for example at the end of an arduous dedicated work or tapas to a devotee as a boon.
It is possible to believe in it without remaining skeptic. Sri Ramakrishna Paramahansa took upon himself (He received, not transmitted a malady, may be cancer, from a devotee that he suffered at his Samadhi time. So also Sai Baba of Shirdi showed his devotees and even disbelievers many instances of such miracles. He declared the Spiritual energy can be effectively transferred, responding where trust and belief are present even after SaiBaba ceased to mortally exist. In the Thyagaraja movie overflowing energy of the musician could effectively cure the sick by his prayer and sympathetic wishes. So did Jesus of Nazereth..it seems to be a phenomenon of pure spirit and associated with no faith in particular.
As for power delivery through Astras a Mantra is invoked into an arrow before releasing the bow to shoot in war.. for spreading water or fire as a missile or for killing enemies in combat is well known in mythology. Sitha matha threatened to slay Ravana if he violated while captive just using a blade of grass.
The energy can be directed to an Astra or another person. It is activated by the recipient when the Mantra is invoked. The Source/Giver repeatedly transfers or transmits spiritual energy for a good cause or destruction in war as may be intended or desired.
Have such miraculous events been in evidence in recent times? Is it a form of telepathy? For example during Maha Kumbh Mela by some Yogis? Or is such power lost out in the Kali Yuga?