Tap X repeatedly to use the Spirit Flame!
Spirit Flame is the very first skill Ori learns, and one of only two skills obtained through a Story Event and not an Ancestral Tree. Learned when Ori discovers Sein in the Sunken Glades, Spirit Flame allows Ori to fire its light at an enemy. And, provided certain abilities are present, even multiple enemies at once!
The speed and damage of Spirit Flame can be increased by upgrading the Ability Tree on its Offensive Branch.