Indra is the lord of the ten sensory perceptions, Indriyas.
Jnanendriya, perception: seeing, hearing, smelling, tasting, touching.
Karmendriya, action: speaking, grasping, walking, excrete, procreate.
He also works for us. When we go into meditation, want to calm our sensory perceptions, want to bring them under control instead of being their slaves, then Indra rebels. The mind does not want to be ‚conquered‘, it wants to let the senses run free. That is why it is so difficult for us to find peace in meditation. Indra does everything possible to disturb the meditator.