He knocked over his smurfin' light lantern that he was praying to for another cycle of the zodiac's worth of life (12 years). That and the whole traitor thing was the justification for it.
Of course, neither of the those events actually happened in history. Zhuge Liang didn't try to magic his way out of death and Wei Yan was loyal to Shu right up till the end.
And yes, late-Shu characters don't look fun to play as. I took one look at Liu Chan and knew I wasn't going to like him.