What epic spells has Mostin's player in mind for when he gets that far?
Looking at his character sheet the DC would have to be at about 45 in order to be completely sure, higher if he got some spellcraft-boosting item. But otoh the DCs usually get ridiculously high, if one tries to recreate all effects faithfully and without resorting to NPC-only tricks
(Dark Subsumption, Limitless Reservoir)
Also as a
planeshift is not sufficient to get to the Far Realm, does it work to get out of there? Because shunting offending enemies into the realm of bubbling and blaspheming insanity must certainly be a nice way of dispatching them and well within the usual levels of magic.
It could also be interesting to use an epic spell to translate a foe to the Far realm and keep him there. Unfortunately without mitigating factors the DC becomes rather high (transport 27, unwilling +4, touch to target +4, cast as standard action +20, ward +14, prevent
gate +16 =
85) and the spell would still have to overcome SR and saving throw.
With Shomei's bracelet he could probably pull this off ... and after 24 hours in the far realms enemies won't be very happy ...
Still, an epic calling of pseudonaturals might be more gainly ...