Help me challenge a berzerk deity

[Endril]

I plan on running a game in the near future with characters that were put down a few years ago after receiving their first divine rank. I want it to be noted that this wasn't something I handed out lightly; they had been playing these characters for years, they accomplished a lot as epic characters, and their divine rank 0 was accomplished by defeating a difficult published module. I bring this up because I want you all to know it's not normal for me to run a game where the characters are level 28 with a divine rank, but we all think it will be fun to play the characters again after so long, and it will be a fun break from the normal 1st-20th games we've been playing. With that in mind, I want to run a fun game, and I have a good story developing for it; I just don't want them blowing through 40+ CR encounters within a round, or with little effort.

That brings me to a problem I'm realizing I created by giving a divine rank to a frenzied berzerker. He's now immune to death effects. Dispel his buffs, and he's still immune. If he's in a (deathless) frenzy, I can literally think of zero ways to kill him. I realize some of you will tell me I've brought this on myself, either by allowing a frenzied berzerker or by giving characters divine rank 1, but I really didn't have much of a problem handling it until this combination came up.

So my question is how would you challenge this player? I don't want to be able to kill him every encounter; I just want them to know the threat of death is there. If the rest of the party realizes he's invincible, it will either make the game less exciting for them, or they'll just lock him in a room with every monster they fight, or both. I want to be able to kill or disable him at least once in a while. I'm not worried about upsetting him by killing his character now and then, since the party has ways to immediately raise him from the dead (without a level loss) and heal him.

As many of you know, deathless frenzy allows you to continue fighting once your hit points are negative, even below -10, and the quickest way to stop it is with a death effect or a spell that specifically stops frenzies. At divine rank 1, deities are immune to shape changing, ability loss, death effects, stun, paralysis, disintegration, etc, as well as mind affecting effects.

[Malroth]

A higher ranked diety can ignore those immunities, and anything that's not higher ranked is perfectly justified in simply teleporting to a different dimension and buffing themselves untill his frenzy wears off or simply piling on the damage untill he's at -several billion hp and then dies when his rage ends.

EDIT:

Also forcibly teleporting the Berserker to a city he's aligned to is a pretty good way of stopping a frenzied berserker, he'll be forced to attack his own followers untill his fury ends.

[Endril]

A higher ranked diety can ignore those immunities

Thank you for mentioning that; I had missed it. There may be an occasional combat with other beings with divine rank, and they can put him down, at least temporarily, thanks to this detail. I was also thinking forcecage is a good answer. Barring that, it looks like he'll usually be able to beat on mortal fighter-types until his frenzy ends and they're long dead, but that's more a side effect of berzerker than divine ranks.