Is it possible to destroy Sakatha?

In our last session, the PCs really struggled with the boss monster they've come to destroy - Sakatha, the demonic god of the lizardmen.

They hit him with everything they could at least once, and most things over and over again - especially if it gave any sign of doing something to Sakatha.

They also tried every weird gamer move in the book - break his weapon in case that's the key, get him off of his throne in case it is that, stand on the throne, stand on the altar, hit the throne, hit the altar, hit his skull, neck, arms, torso, vitals, legs, feet, and hands in case it is any of those, stab him with a wooden stake (his armor was too tough), Dismissive Wave, Deathtouch, splashing holy water on the altar and throne, Sunlight (which does seem to help . . . but slowly) . . . the only thing that they haven't tried was breaking his crystal ball because I pointed out that it wasn't that.

So apart from Sunlight, which seems to be harming him (but not killing him), what is left to do?

I'm not saying.

I put him clues but I know they were missed - flat-out bypassed or skipped over. And this isn't a fight they can run away from and come back after trying to find them. At this point, it's win or TPK, unless Gerry can somehow sneak out invisibly and get past all of the obstacles in his way.

But what I said to my players by email was, "I'll give one big hint, really - Sakatha is much less of a puzzle monster than it seems. You guys got desperate and started to grasp around for the "thing" that will destroy him and tried all sorts of gamer stuff no GM would ever put in, trying to get a clue on what to do. Just remember that he was potentially defeatable by your original 275-ish point guys, and didn't depend on any special weird ability that someone had on their sheets."

What it would take is still within their grasp, if they can see it and try it. Sakatha isn't giving them any clue how to defeat him - and they haven't tricked it out of him. So they need to figure out how to figure it out before he eventually rolls some nice critical hits and downs people for good. Time is on his side - he's eventually going to hit someone, and they can't make him any more damaged than he is now.

I took the name and inspiration and image from an adventure published by TSR, but the Sakatha of that module isn't the Sakatha of my game. There isn't a hint in that material, in case anyone asks.

In the end, yes, it's possible to destroy Sakatha. There was a reason I though we'd wrap that fight up 1 1/2 sessions ago . . . but what is it? Up to the PCs to figure out before next game, or it'll be a long grind to death.