Tvashtra

Causing wrinkles to form themselves on his brow, sure indications of wrath, the son of Pandu
blew his prodigious conch, called Devadatta, and then he shot the weapon called Tvashtra that is
capable of slaying large bodies of foes together. Thereupon, thousands of separate forms started into
existence there (of Arjuna himself and of Vasudeva). Confounded by those diverse images after the form
of Arjuna, the troops began to strike each other, each regarding the other as Arjuna's self.' 'This is
Arjuna!' 'This is Govinda!' 'They are Pandu's son and he is of Yadu's race!' Uttering such exclamations,
and deprived of their senses, they slew one another in that battle. Deprived of their senses by that mighty
weapon, they slew one another.

Drona Parva: Section 29