So the bodhisattva helps all beings, because he perceives their suffering, but he knows that their suffering arises from ignorance—the ignorance of attachment to things when in fact all things have no ultimate essence (no atma).
These are principles that we already saw in Mahayana. Vajrayana follows these same ideas, and also highlights the role of the bodhisattva. So Vajrayana is in some ways like Mahayana, but it uses more mystical or magical methods than Mahayana.
In particular, Vajrayana employs not only much magical ritual. It also invokes various deities, some of them demonic (fierce and fearsome), as a method to attain a higher state of consciousness.
Fierceness deities can be a good thing if they chase away our ignorance and delusions.