Erfworld/OOTS Commander switch

[Freederick]

Wouldn't work. The sapphire is there to seal a pre-existing rift in the fabric of reality--the rift does not move, therefore the sapphire cannot move either. (This was actually stated in so many words by Hinjo when Roy suggested moving the sapphire somewhere else).

Well, in that case:
1. Pretend to evacuate the sapphire, with controlled leaks of this operation to convince the enemy that it has been moved. At the very least, this would force Xykon to split his forces, going after both sapphires; and the forces attacking the fake one would be drawn into a trap.
2. Seal off the bottom floors of the keep by filling them with stone or fire, etc., making them completely impassable. This would prevent the hobgoblin army and Redcloak from reinforcing Xykon in the throne room, and effectively split Xykon away to be dealt with by the righteous undead (for lack of a better term).
3. The remainder of the plan, drawing the hobgoblin forces into house-to-house attrition, is still applicable.
4. Separate the high-level adventurers into a strike force with high mobility (flying carpet?) so that they could intervene where most needed, withdraw, strike surgically again. This maximizes their punch.

Note: this last part resembles the way Parson is using the Dwagons and warlords.