According to what I read from Buddhist text, Mahayana Buddhism was started by 龙树菩萨。 The sage had 定功 which enabled him to travel to other realms like heaven and hell. During one trip to heaven, he attented dharma talk by the Buddha on, i believe, the Diamond Sutra (金刚经) which he later brought back to earth. Then there was once he visited 龙宫 and discovered a collection of Buddha's 华严经, which he also brought back to earth. I believe the intention of the Buddha is as such, he began by preaching the Hinayana, once the followers had built up a strong foundation, he then introduce the more advace Mahayana to the followers through other channels. Mahayana is meant for 天人 and was too advance for human, but is appropriate once human mastered the Hinayana. There are actually many 方便法门 taught by the Buddha, sages and angels. The 仙丹 is one, but this method has to be practiced together with moral cultivation and spiritual training. 仙丹is able to let people momentarily 'cheat' death or karma, but the students have to use these moments to 忏悔 and 修行 in order to gain awakening. However if the practitioners cheated karma and use the borrowed time to commit more sins, the end results will be much worse. As such, these 方便法门 are only suitable for students who are very committed and advance in their training, these 方便法门 will act as the nudge needed to help these students overcome the final hurdles.
I will recommend to say conservation of energy and matter. Every entity is duality of matter and energy. That is depended on the percentage of matter and energy. Or, simply say matter is a form of energy. Energy with good morality is god. Energy with bad morality is evil. How is that! Info only. Just to say something. Have a nice day.