Vasavi Shakti (vāsavī śakti)

The Vasavi Shakti is the infallible spear Indra gives Karna in exchange for the golden armour and earrings he was born wearing, on the condition that it can be used once and then returns to its giver. Karna hoards it for years, saving it for Arjuna, and Krishna spends much of the war engineering situations in which he might be forced to spend it. On the fourteenth night Ghatotkacha becomes unstoppable and Karna throws the spear to save the Kaurava army, killing him and disarming himself for the duel that matters.