By cheating horribly with leadership, fusion, schism, and appropriate buffs.
The cleric is a cleric of trickery. He'll therefore use a miracle'd simulacrum to puppet-talk before the king. For someone with his level of bluff, swapping himself out at his initiative go should be trivial (a psychic tattoo of dimension swap will resolve it.
His simulacrum should be prepared to simply counterspell (via dispel magic or greater) whatever it can until it's popped. Appropriate illusions and mirror images should keep the question of "is he dead?" open, and of course the epic cleric will ensure that the victory condition is something gameable rather than "to the death".
Thus, the first round of combat will be spent by the "real" villain buffing short-buffs via a time stop, and watching the party alpha-strike a statue (or three) of snow and ice.
It's also worth noting the leadership feat, simply for the absurd resources it gives an epic character in terms of lackies who exist to buff him at the start of every day and to enchant custom items for him. The real trouble here is that you can spend hours on figuring out buffs (and should) especially with extend spell (and any other meta-magic feats you allow) and the combat will be over in 2 rounds, give or take.
Still, the best way to open is to make the cleric's cohort be an epic level psion, fusioned into the cleric. Then, as the cleric is talking, the psion can be buffing the fusion to a sufficient degree. As an extend-power fusion lasts for 43 minutes, it's trivial to find enough time to recast it every so often. With the chain of leaderships being the case (as there's no reason for the cohort not to have leadership) the available budget is far greater than 150kgp.
The fusion'd psion allows for adequate teleportation/anti-teleportation (note divert teleport and teleport trigger to keep the cleric "around" long enough to play with his food. With psionic moment of prescience it's gravely unlikely that the party will win initiative, and if they do, the fusion can just fate of one it. (and so on and so forth with dispelling buffer and so on..)
Disjunction ruins everyone's day as it forces the entire table to an evening of recalculation. You should already have a agreement in place for "no first use." Still, with the resources of leadership on hand, it should be trivial indeed to figure out a list of buffs and magic items that fit your needs, prevent the rogue from pulling off a sneak attack (i.e. an incarnated ubiqutious vision and improved unncanny dodge from danger sense. With Schism running it should be trivial to get enough buffs up in time while under a time stop.)