After Malcolm thawne discovered his connection to Flash/Barry Allen, he felt cheated for the life. Filled with age towards Allen and towrds his own family, he searched help in his adopted grandmother, who saw in him what she found lacked in her own blood. By magical rituals, she and Malcolm encased all the power of the blue flame, a magic used by the Thawne family into a cold blu gem, feed by the hate of Malcolm himself towards the Flash. Using the power of the gem Malcolm would fight against the Flash in his demential search for retribution.
The hate of Malcolm for Allen would be pass to the next generations and for centuries the Thawnes would use the power of the gem to fight against the Allens. The final gambit of the Thawnes would put existance itself at risk but the quick action of Wally West would defeat the power of the hate accumulated in the gem by giving to Malcolm what he wanted most, by pushing him to the Speedforce field.