He came to power by uniting many of the nomadic tribes of Northeast Asia. After founding the Mongol Empire and being proclaimed "Genghis Khan", he started the Mongol invasions that resulted in the conquest of most of Eurasia. These included raids or invasions of the Qara Khitai, Caucasus, Khwarezmid Empire, Western Xia and Jin dynasties. These campaigns were often accompanied by wholesale massacres of the civilian populations – especially in the Khwarezmian and Xia controlled lands. By the end of his life, the Mongol Empire occupied a substantial portion of Central Asia and China. 

Before Genghis Khan died, he assigned Ögedei Khan as his successor and split his empire into khanates among his sons and grandsons. He died in 1227 after defeating the Western Xia. He was buried in an unmarked grave somewhere in Mongolia at an unknown location. His descendants extended the Mongol Empire across most of Eurasia by conquering or creating vassal states out of all of modern-day China, Korea, the Caucasus, Central Asia, and substantial portions of modern Eastern Europe, Russia, and Southwest Asia. Many of these invasions repeated the earlier large-scale slaughters of local populations. As a result, Genghis Khan and his empire have a fearsome reputation in local histories.
Who founded the Mongol Empire?
Who did he assign to take over after he died?
How did Khan come to power?
Where did the Mongols raid?
Were they nice to the civilians?
When did the founder of the Mongol Empire pass away?
After doing what?
Who did he defeat shortly before dying?
Where was he laid to rest?
What is the Mongol's reputation in history?
Genghis Khan
Genghis Khan
Ögedei Khan
Ögedei Khan
by uniting many of the nomadic tribes of Northeast Asia
 by uniting many of the nomadic tribes of Northeast Asia
the Qara Khitai, Caucasus, Khwarezmid Empire, Western Xia and Jin dynasties
 the Qara Khitai, Caucasus, Khwarezmid Empire, Western Xia and Jin dynasties
no
massacres of the civilian populations 
in 1227
 in 1227
after assigning Ögedei Khan as his successor and splitting his empire into khanates among his sons and grandsons
assigned Ögedei Khan as his successor and split his empire into khanates among his sons and grandsons
the Western Xia
the Western Xia
in an unmarked grave somewhere in Mongolia at an unknown location
in an unmarked grave somewhere in Mongolia at an unknown location
they had a fearsome reputation
a fearsome reputation