Karna Vasavi Shakti

As you know, in Apocrypha, Karna's form is always his first ascension form in the game. When he is about to use vasavi shakti, however, he changes into what we know as his third ascension form in game. If his first ascension form is equipped in game, does he use vasavi shakti with his first ascension lance? Or does he morph into his third form to launch it?