After causing the deaths of millions across the universe, the megalomaniacal and sociopathic alien warlord Ch'rell (whose aliases include Torrinon, Kako Naso, and Duke Acureds) was captured by his fellow Utrom and being transported back to his home world to answer for his crimes. However, Ch'rell managed to escape captivity and sabotaged the Utrom ship, causing it to crash-land on Earth during the Sengoku period of feudal Japan. Stranded on the then-primitive planet, the Utrom were forced to wait for centuries until human technology advanced enough for them to develop a teleportation device and return home. They thus developed humanoid exo-suits to hide amongst the humans, and Ch'rell stole the first working prototype and used the Japanese legend of a Demon Tengu to craft a dual identity, becoming a wealthy Japanese philanthropist named Oroku Saki while secretly operating as the crime lord known as the Shredder. Saki soon founded the Foot Clan, which grew into a massive underground criminal empire by the 20th century, and created important links with the New York underworld, especially with the Purple Dragons; their leader Hun would serve as his right-hand man. Saki also adopts an abandoned girl named Karai, whom he personally trained in the arts of ninjutsu to lead the Foot Clan in Japan while he operated in New York City. In New York, the Shredder captures Hamato Yoshi, one of the Utroms' foremost guardians, and kills him after he refuses to reveal their location. Yoshi's pet rat Splinter witnesses his murder and escapes, winding up in the city's sewers where he and four baby turtles are accidentally exposed to a mutagenic ooze created by the Utroms, transforming them into sentient humanoid lifeforms.