Aluka is a special exist in Zaoldyeck family, he have no Nen ability but can control everything even make dream come true, but in return, someone will die for his desire. In Aluka's rule, there
is no any difference but Killua, because for Aluka, Killua is a special exist. Killuan treat him as a normal boy, but his brother and father just seems him like a tool.
In order to save Gon's life, Killua try his best to bring Alika to the hospital and escape from the hunting of his brother Yelllmi. After cruel the injury of Gon, he decide to face Yellmi alone and directly. Yellmi also jnow some rules of Aluka and he infer that the key of control Aluka's ability is Killua. He even know the unique man who can out of the Aluka's rule is Killua. So he threat Killua and told them taht he will kill anyone who want to disturb his plan. But Killua use his own way to prtect Aluka and in order to prevent "the thing" come back, he ordered " the thing" send Yellmi back to their family and have a talk with "the thing". He know the thing" just feel longly and want someone play with him. And the man who punishment by that ability is just due to their desire.
"The thing" can understand the mind of Killua and promise that he will never appears again then cried. When Aluka return to his own mind, he said that nobody can bully "the thing" and want Killua can appoligize to him. Killua know the truly idea of "the thing" and promise that he will protect both Aluka and "the thing" forever!