Ilkhans are of Mongolian origin Dynasty, most famous of them is Genchis Khan and his infamous Grandson, Hulagu Khan. The later, Hulagu, is well known for his Cruelty and barbaric tactics, the most evident example, is the sacking of Baghdad in 1258 AD ( 656 AH ), when he extinguished up to 1,000,000 soles of Baghdad occupants in one week of killing rampage by his solders, and making Tirgis river waters Black/red from books he threw in , with the bloods of the innocent slaughtered.
Just to show how uncivilized this dynasty was, they adopted the monitory system of every place they invaded, as they themselves had no civilization to rely on in this respect.
Unfortunately, The Abbasid Caliph, Al-Musta'asim, did not prepare for this influx of human Locust, his army destroyed and Baghdad surrendering to these blood thirsty riffraffs. The Caliph himself was rolled in a carpet, and was trampled on by horses, all his sons bar one was killed, and to show, yet again, the cruelty of the ilkhans, they made the Caliph watch as his family and his subjects getting murdered in front of his eyes, his city, the cradle of civilization for several hundred years, getting burnt to the grounds.

Please note that the period After Abu Sa'id is known as -Rival Khans - that is why you will notice that some dates are same for 2 different khans