Tōga

was a powerful daiyōkai who was known throughout feudal Japan as the fearsome Lord of the Western Lands. He fathered two sons, the second of which was the hanyō Inuyasha from the human woman Izayoi. His first born son was the daiyōkai Sesshōmaru from an unnamed demoness. 200 years before the shattering of the Shikon no Tama, he stopped the invasion of a Mongol army lead by the Lord Hyōga and his son Menōmaru. Around the same time he defeated the Panther King after he and his tribe attempted to take over the western lands he ruled.

He had many adversaries during his lifetime, and many of them have ended up crossing paths with one or both of his sons many years later.

History
In the third InuYasha film, the Great Dog Demon survives long enough to save Izayoi and their newborn child Inuyasha; still weak from his battle with Ryukotsusei, he dies defending them from a human foe named Takemaru. The gateway to his tomb is hidden in a black pearl (a mystical gem that creates a path between the mortal and spirit worlds) inside Inuyasha's right eye, which was created by Hosenki, an oyster demon, on Inu no Taisho's command. Within the pearl, their father's body is shown as an enormous dog skeleton in a suit of armor: his true form, according to Myoga. The sword Tetsusaiga, forged from the Great Dog Demon's own fang, rests inside this cavernous skeleton, protected by a barrier that repels any non-human with malice toward humans. Because of this, Inuyasha inherits the sword rather than Sesshomaru. This also suggests Inuyasha's father was never bigoted toward humans nor was he evil. Sesshomaru even says that he had a "merciful heart for humankind." It seems that he did have a sense of honor and perhaps wanted both his kind and the human race to live in peace.



However it should noted that what he did after defeating Ryukotsusei such as his last meeting with sesshomaru and saving inuyasha was in the 3rd movie only and therefore is non canon. That also includes the humanoid and dog form the movie shows.

Abilities
Much of the Great Dog Demon's abilities are unknown, but it is known that he could change his appearance to resemble that of a human's, much like Sesshomaru. His true form was that of a gigantic dog which was far larger then both Sesshomaru's and Sesshomaru's mother's true yokai form. This allows him to move at top speed. He has been stated to be one of the most powerful yokai in the series by Myoga and Totosai. Despite his great power, he was unable to kill Ryukotsusei and was only able to defeat him by sealing his powers away. The aftermath of the battle led to the dog demon's death. By the end of the series both his sons, Sesshomaru and InuYasha, surpass him, though not in raw strength, but in their abilities to fend for themselves without the need of his protection.

He was arguably the most powerful yokai in the series, shown by Sesshomaru's desire to surpass him, revealing that the Daiyokai was far stronger than Sesshomaru himself. He also commanded the three swords of Supreme conquest: Sō'unga, Tetsusaiga and the Tenseiga, effectively giving him the ability to manipulate the dead, the ability to resurrect the dead, and the power of destruction. He also is shown wielding the Tessaiga and the Sō'unga quite easily, confirming his power. He is even shown handling the Tessaiga deftly, summoning two ferocious wind scars, destroying a fort. Totosai also said Inu no Taisho could summon a perfect Meido Zangetsuha sphere in only his third try, a feat which requires a huge amount of yoki.

Aside from his immense strength, the Great Dog Demon of the West also had an incredible power of foresight, with some of his actions having a hidden message behind them. He entrusted the Tessaiga to his son Inuyasha, accurately predicting that he needed the sword to protect himself, as well as another, namely Kagome. He bequeathed the healing sword Tenseiga to his eldest son, Sesshomaru, in order to teach him compassion. Totosai eventually reforged the Tenseiga into a weapon, giving it the ability to perform the Meido Zangetsuha, presumably on Inu no Taisho's orders.

It can be assumed that the Great Dog Demon was capable of creating barriers as he was able to put a barrier on Tessaiga.

Relationships

 * Sesshōmaru's mother: She was his first wife and had Sesshomaru as a child, but he left her for Izayoi. She was seen in the manga and she then appeared in the anime's second series, InuYasha: The Final Act. Also being a daiyokai like her husband, she can also transform into a giant dog.
 * Izayoi: It is unknown when they first met, but they ended up falling in love and having a half-demon child, InuYasha. After his last battle, he rushes to save her without first tending to his wounds. He fights through the soldiers only to find her already dead. Using the Tenseiga, he brings her back to life, giving her the Cloth of the Fire Rat, and tells her to escape with their newborn son whom he names InuYasha. His last words were: "Izayoi...You must live. Live a long life. Live long and well with Inuyasha." This showed that the Great Dog Demon did deeply care about his sons, not seeing them as tools of heritage.


 * Inuyasha: being born only moments before his father's death, Inuyasha never met his father. In Swords of an Honorable Ruler, after saving Izayoi from Takemaru with Tenseiga, he named his son Inuyasha. According to Myōga, Inuyasha is able to use his sword Tessaiga because he protects Kagome, who is human, mirroring his relationship with Izayoi. Many say that InuTaisho is a two timer like Inuyasha because he mated with Sesshomaru's mother and fell in love with Izayoi and Inuyasha fell in love with Kikyo (who dies) and then Kagome (who later becomes his wife). Like InuTaisho cutting off Takemaru of Setsuna's left arm, Inuyahsa cuts off Sesshomaru's left arm. So maybe that is what Inuyasha also inherits from Inu no Taisho.
 * Sesshōmaru: The InuTaishō's relationship with his first son was somewhat strained because he left his mother for Izayoi. In Swords of an Honorable Ruler, one moonlit night, his gravely injured father asked him if he had "someone to protect". Sesshomaru knew that it was his father's final test for him, and Sesshomaru stated that his answer was "No". So, the Tenseiga was passed to him after his father died saving Inuyasha and Izayoi. At first Sesshomaru felt nothing for the Tenseiga as it had no destructive power whatsoever, but as time passed, he started to understand and respect its power. He also came to understand his father's cryptic words. Upon meeting the human child Rin, his attitude toward humans changed. Sesshomaru felt he should protect the young girl. With something to protect (Rin, Jaken, and sometimes Inuyasha), Sesshomaru became a very powerful daiyokai, just as his father intended for him.


 * Ryukotsusei: a dragon demon with powers that resemble lightning. Inu no Taisho only managed to seal him to a cliff with his claw. According to Myoga, Ryukotsusei was much too powerful to kill. It is implied that the wounds Inu no Taisho received in that battle led to his demise during his battle with Takemaru of Setsuna in the third movie. Many years later, Naraku releases Ryukotsusei's seal hoping the dragon would kill Inuyasha, who was there to defeat Ryukotsusei.


 * Hyoga: a moth demon from "the Continent", or as some have inferred, China. This is yet another demon that Inu no Taisho managed to seal but not defeat. Sealed within the Tree of Ages, Hyoga is absorbed by his son and successor Menomaru, who in turn tries to kill Inuyasha and absorb all living souls on earth.


 * Shishinki: the original wielder of the Meido Zangetsuha. The battle between him and Inu no Taisho is implied to be inconclusive though it is revealed Shishinki was terribly injured. He seeks to kill Inuyasha and Sesshomaru as revenge for stealing his technique.


 * Panther King:: a demon that Inu no Taisho manage to defeat long ago. He was revived by his tribe using sacred jewel shards. The panther king was destroyed by Inuyasha and Sesshomaru.

Quotes

 * "Izayoi...you must live. Live a long life. Live long and well, with Inuyasha."


 * "And if will you kill me: your own father?"


 * "Do you desire power so much."


 * "Surpreme...conquest. Tell me Sesshomaru, have you someone to protect?"


 * "That doesn't matter...I cannot afford to lose her! Besides, I am not long for this world."