How did Xykon survive his fight...

[zimmerwald1915]

Actually, the Empowered Sunburst would deal 37d6 damage assuming Darth V's caster level counted as 25 or above. Empower multiplies the "x" in the expression "xd6", not the damage put out by the dice. Still, Xykon did make his reflex save. Thus the average damage dealt would be 64, and the minimum damage dealt would be 18.

The Crushing Hand would deal 2d6+12 damage, for an average of 19 and a minimum of 14.

Superb Dispelling would deal 10d6, for an average of 35, and a minimum of 10.

Explosive Runes would deal 6d6, for an average of 21 and a minimum of 6.

The average damage Xykon would have taken would have been 139 HP, and the minimum damage would have been 48. Xykon's average HP total, assuming he's level 21 and not level 27, is 136. His average HP total at level 27 is 175. Rich, from what I've been able to tell, tends to throw minimum spell damage at V and to give her near-max hit points per hit die. There's no reason he shouldn't extend the same courtesy to Xykon, particularly given the latter's lack of a CON score. In any case, it's perfectly believable that Xykon would survive his fight with Darth V.