All spiritual warriors have what is known as a phantasm, an ultimate attack of sorts that also makes them unique as a warrior.
Aquin's sword transforms, and when he is faced with a demon that towers over him, this is a special Phantasm designed for dealing with large entities. He can fling his sword like a boomerang or a missile, using pure psychic energy. The sword strikes the targets vitals and power sources, immobilizing the enemy. Even if the enemy would be more powerful then Aquin, this technique ensures victory.
This sword gives Aquin nearly god like ability, but it burdens him and he hates it with a passion. He dreams of being rid of the sword one day and hopes that he will be able to pass on his power to the right person. If not, this thing will one day be his demise.
