Niko

Niko appears as a small boy of common birth, most often shown with the loyal stray dog that keeps at his side. Game material depicts him in ragged poverty, treated as an outcast by his own neighbors. After he is transformed into the Heart of the Great Tree, that frail child is buried inside a monstrous apostle whose only weapon is a devastating scream, leaving almost nothing of the boy behind but a remnant of his torso.

Kind and simple of heart, Niko meets a life of nothing but hardship with a persistent smile, grateful merely to be alive. It is said that he would never dream of hurting another soul, even as the villagers around him repaid his mere presence with hatred. Supplementary notes describe him as a sorrowful apostle who, unlike the others of his kind, harbors no malice toward humanity at all and instead longs only for peace and happiness, marking him as a truly singular being.

Niko lived in a village where he survived by taking scraps from the villagers' crops, and they answered his hunger with beatings, striking him with sticks and pelting him with stones. He took shelter on the steps of Eriza's church. When winter came and the harvest failed, he was left at the edge of death, and no one in the village would lift a hand to help him. Gathering his last strength, he reached the church, but Eriza never heard him over the pealing of the New Year's bells, and he collapsed at its doors with his dog beside him and a beherit clutched in his left hand.

When Guts later rushes toward Eriza's church, he finds that Niko has become the Heart of the Great Tree and must face both the boy and Eriza. Once the battle is over, with Gyove's forces setting upon the village, the still-living Eriza casts herself into the flames while cradling the last human piece of Niko that remains. The beherit he once carried passes on through others, taken by Rita from his village to Balzac's castle, where Balzac makes use of it.