Answers 1. Sirius insisted that Kreacher could not be set free because he knew too much about the order.
Because of their safety. Kreacher had heard a lot of conversations that had gone on in his presence. When he wasn't free he couldn't tell these secrets to Voldemorts support. If he'd been freed he would be able to do this.
Kreacher's joy at being given a Black family "heirloom" as his own caused him to drastically change his view of Harry. He even started to treat Hermione, whom he had previously disdained as a "Mudblood", a bit better. Hermione turned out to be right about Kreacher; he was nice to those who treat him well.
Kreacher disliked Sirius because Sirius thought differently to his ancient family, and Kreacher had the same views as his masters and mistresses. He couldn't think for himself, and that's where he and Sirius were so very different. Kreacher was mistreated by Sirius for many years because of this.
Kreacher was a male house-elf who served the House of Black with fanatical loyalty for most of his life, until he was left to Harry Potter upon the death of Sirius Black in 1996.
Kreacher was not however fully able to betray the Order because he wasn't their protector and couldn't say where the House of Black was. Kreacher however sold enough information to get Narcissa knowing that Harry loved Sirius and would go to protect him from Voldemort in a possible hostage crisis.
The potion, (the same one Dumbledore drank) caused Kreacher to have nightmarish delusions, intense stomach pains and made him dehydrated. Voldemort then left, leaving Kreacher to drink from the lake (as any water conjured evaporates) and die at the hands of the Inferi.
The Black family elf Kreacher did not have any love for many people other than his master. However, as hateful as she is to most people, Bellatrix was always very kind to Kreacher. In fact, Kreacher even kept a picture of Madame Lestrange by his bed because of how kind she was to him.
Voldemort took Kreacher to the Crystal Cave and forced him to drink the potion in the basin so that Voldemort could place Salazar Slytherin's Locket in the basin. The potion, (the same one Dumbledore drank) caused Kreacher to have nightmarish delusions, intense stomach pains and made him dehydrated.
"The horcrux amplified the negative emotions that Ron had and similarly it makes Kreacher hate mudbloods even more and disrespect Hermoine way more than he would have if he didn't have the horcrux," kaptinkracker concludes.
After Sirius' death, Harry Potter became Kreacher's new master. Kreacher disliked Potter and neither did Potter like Kreacher. When Albus Dumbledore came to Privet Drive to tell Harry what Sirius had left him, which included Kreacher and Grimmauld Place Twelve and all his belongings.
He thought that if he called Kreature, Death Eaters might also come with him.
Dumbledore seemed to have terrible nightmares or visions, and was almost too weak to stand up after drinking the potion. Kreacher said that when Voldemort forced him to drink the emerald potion his "insides burned" and he saw "terrible things" (DH10).
We have learned that a House-Elf can be freed if given clothes by his or her master, but Hermione is not their master, and so accepting clothes from her will not free the elves.
He was just a house-elf for heaven's sake. Some would say Regulus simply treated Kreacher with the same level of respect as another human. The Golden Trio demonstrated how Kreacher does when he was treated with respect, with the Black House getting cleaned, actually cooking, and not slinging insults.
Master Regulus volunteered Kreacher to assist Voldemort who then took Kreacher to a cave, forced him to drink a basin of burning potion and left him for dead. The elf had been used to test the defences for a locket bearing the symbol of Slytherin. Unbeknown to Voldemort, Kreacher escaped and returned to Regulus.
Weaknesses. Like his family, Regulus was easily swayed by Lord Voldemort's "pure-blood" rhetoric. He learned too late that the Lord Voldemort's beliefs were far more evil than he had ever realized and being a Death Eater involved far more unpleasantness than he was capable of.
It is very likely that Lord Voldemort was not thinking along the line of it being the same house elf. It is stated that Voldemort did not know and couldnot comprehend that house elves would have magic that he does not.
While Arthur lived to tell the tale, others were not so lucky. Lord Voldemort callously fed Muggle Studies teacher Charity Burbage to Nagini after performing the Killing Curse. Sometimes Voldemort simply let Nagini do the dirty deed herself. The most famous example of this is Severus Snape.
She married Rodolphus Lestrange after leaving Hogwarts "because it was expected of her" to marry a pure-blood. However, Rowling stated in an interview that Bellatrix truly loved Voldemort.
As Kreacher was not the Secret Keeper, he couldn't have given the location of the Order's HQ to either Bellatrix, Narcissa or anyone else. As Albus Dumbledore was the Secret Keeper to 12 Grimmauld Place, only he would be able to divulge the location.
2. She Had A Child With Voldemort. During Harry Potter and the Cursed Child, it was revealed that the affair that Bellatrix had with Lord Voldemort actually resulted in the birth of their illegitimate child, Delphini.
Therefore, when Regulus Black gave Kreacher the horcrux to hold onto, it turned Kreacher bad. The horcrux amplified the negative emotions that Ron had and similarly it makes Kreacher hate mudbloods even more and disrespect Hermoine way more than he would have if he didn't have the horcrux.
Why didn't Regulus Arcturus Black made Kreacher drink that potion in the basin? Kreacher was powerful enough to absorb its effects and could apparate them both out of the cave.
According to the WOMBAT test, it is possible that house-elves have an average life expectancy of 200 years, cannot be ordered to kill themselves, breed infrequently and only with their master's permission, can override wizard enchantments, and have an allegiance to their home rather than its inhabitants.