Hi! I have a question regarding the usage of astras in Hindu mythology. How did a sage choose who to pass down a particular Astra to? Did it depend on caste, with only Kshatriyas and Brahmins allowed to use astras, which is why there was such a great uproar when Karna, believed to be of low caste, was able to summon a variety of astras? But that still doesn't explain the discrepancy between the number of astras a particular Kshatriya or a Brahmin could summon. Like in the Mahabharata, Arjuna, Karna, Bheeshma, Drona, etc lead the pole with respect to number of astras known, and other warriors don't know as many astras as these people do. Which is confusing, because if only Kshatriyas and Brahmins could use astras, then ideally shouldn't all members of both these castes know the same amount of astras? I've seen some sources suggest that astras were handed down only following the establishment of a pupil's character, irrespective of the pupil's caste, because these weapons were so destructive and couldn't just be entrusted to anyone. This explanation does work, except we've already seen this condition violated in the Mahabharata, and without repurcussions to the offender! Drona refuses to teach the Brahmastra to Karna, but caves in to one single pair of puppy-eyes from Ashwatthama, despite knowing he didn't really deserve this knowledge and couldn't be trusted to use it responsibly. And Ashwatthama does go on to use the Brahmastra for less than noble purposes! So how exactly did any sage choose who to pass down an Astra to?
This is an excellent question, and this is my best understanding:
So, for all intents and purposes, astras are more equivalent to cheat-codes for a video game rather than physical weapons (which...you probably already knew lol). And just so, you could end up with an astra from a variety of sources:
direct from the source (ie, from the god who possessed it. Arjuna is the best example when he picks up special weapons from Shiva and Indra after meditating long enough to earn it)
from your teacher, buuut only if he liked you enough (and it was within his rights to pass it on or deny it for any random reason! Like you said, Drona gives it to Ashwattama and but refuses to teach Karna not because of caste, but because he wants Arjuna to be the best. And as annoyed as Karna is, his only options within that society is to go elsewhere)
from a random rishi you pleased/impressed/helped (Rama gets pretty much every divine weapon there is from Vishwamitra after helping to protect his sacrifice
So there doesn't seem to have been any quality control on who actually got the astras, just who you ran into; which is also how villains as well as heroes all seem to possess them. Until the Mahabharata war, it seems to have been chaos--until then the majority of the people who posessed the weapons either died before htey could pass it on any further, or (horrified by the damage) presumably decided to never to do so anymore. Which arguably might have been a secondary goal on Krishna's part.