Eu tenho um jogador em minha campanha que pegou os Flames of Phlegethos fazendo proeza racial ( do Guia de Xanathar para Tudo , p. 74-75). Uma de suas habilidades é:

Whenever you cast a spell that deals fire damage, you can cause flames to wreathe you until the end of your next turn. The flames don’t harm you or your possessions, and they shed bright light out to 30 feet and dim light for an additional 30 feet. While the flames are present, any creature within 5 feet of you that hits you with a melee attack takes 1d4 fire damage.

Além disso, ele pegou a produzir cantrip:

A flickering flame appears in your hand. The flame remains there for the duration [...]

You can also attack with the flame. When you cast this spell, or as an action on a later turn, you can hurl the flame at a creature within 30 feet of you. Make a ranged spell attack. On a hit, the target takes 1d8 fire damage.

Se ele lançar o produzir chama cantrip e o mantiver (isto é, não atacar ou tentar causar dano com ele) isso ainda acionaria essa habilidade Flames of Plegethos ?