Class and Level Geekery XVIII - Everyone's an Expert

[Squire Doodad]

Also while Greater Plane Shift would work - 8th-level spell, it was first printed in the Planar Handbook and reprinted in the Spell Compendium - I don't think that's actual proof that he can do that on his own power. Remember he took Redcloak and the MitD to the astral fortress? If he could do it on his own, he'd just cast the spell himself. That's what he does with teleportation. Instead, he gave Redcloak the coordinates, who opened a Gate for that.

Well, keep in mind that he needed Redcloak to fire off some spells, and Xykon likely had a massive slew of spells of his own to fire off.
He may well have only had his most important daily spells queued, and then everything else was for the fortress. Gate is high-level, which means getting Redcloak to cast it for him can open up quite a bit of room.