Finally figured out what the throne did besides zapping you for HP damage. If the magic of the throne overwhelms you, you receive a +1 increase to one of your stats (STR, INT, WIS, DEX, CON, CHA etc.) or -1 decrease to one of your stats if you are unlucky.
Of course this Seat of Stat Altering can be manipulated by saving the party before taking the seat, a bit of patience and reloading if you end up with a stat decrease.
Greyhat before taking the throne
Greyhat after taking the throne
Per my post of sometime last year, the fountains that you find in the dunjons will either replenish your HP’s to their full amount, or poison you if you are unlucky.