Raajasooyam was the name of an elaborate sacrifice performed only by kings. A king performing Raajasooyam was aclaimed as emperror those days.
In ancient times, Harishchandra was said to have performed this. Later, Yudhishthira performed this sacrifice.
It was said that its successful completion leads to a large scale destruction of kings and masses. Also, its procedures prescribe that the king who performs this sacrifice should play a game of gambling with his near and dear, as a part of its routine rituals. It is interesting to note that Yudhidhthira palyed dice game with Shakuni after the sacrifice and its successful completion resulted in a heavy destruction of the kngs and their forces within fifteen years.