Rictor/Siana/Ari
The fact that Rictor had jumped in front of her was fortunate -- she had her armor, such as it was, but she did not doubt that even with protective effects, that blow would have knocked her from her feet. She scrambled back, grateful that her song had been winding down.
This creature was clearly tough; even with the knight and samurai attacking it from both sides, it hardly seemed fazed. Well... perhaps there was something to be done about that.
She attempted to stay out of the way of the various weapons as she modulated, the bright, martial strains of Battle Song ringing out to strengthen the fighters and imbue them with Bravery. Perhaps with additional strength, they would take the headless creature down before it could injure them further.