Sankai (meaning “birth monster”) is known as kekkai in Saitoma Prefecture and Kanagawa Prefecture and kekke in Nagano Prefecture. The legends regarding its out appearance are sparse, but it is said to look like a cattle and is hairy. After birth it’s said to bury under the house to kill its mother. In Urawa, a practice existed of surrounding the bottom of a house with byōbu during childbirth to prevent this from happening. If the kekkai successfully escapes, the mother will die. In order to prevent this someone would have to guard the hearth usually with a shamoji.
Hellhounds are know all around the world. They are supernatural dogs based in folklore and mythology. The features that are usually attributed to hellhounds are black mangled fur, glowing red eyes, super strength or super speed, phantom or ghostly characteristics, and a foul smell. Some European legends say that if you stare into the eyes of a hellhound three or more times you will die (I’ve heard if you look once into their eyes you’ll die or a loved one will die as well). Also in those legends, if you see or hear one howling it may mean death as well. In some cultures that associate hell or the afterlife with fire, hellhounds will have fire-based abilities and appearance. They often are said to have the duty of guarding the entrances to the world of the dead, such as graveyards and burial grounds, or take on other duties related to the afterlife and the supernatural, such as hunting lost souls or guarding ghostly treasures. Some of these supernatural dogs, such as the Welsh Cwn Annwn, are regarded as benign, but still encountering them was a sign of imminent death. The most famous hellhound would have to be Cerberus from Greek mythology.