I have tried many times to beat the Ancient Crystalline Golem in the Lost Grove caverns. And every time it ends with my entire party being knocked unconscious.

It generally goes well until the Golem gets to full mana and has the exploding crystals. I can't do anything against those as far as I know, and it knocks my pets unconscious immediately.

For reference, here is my current party, who I've never had an issue with before:

1: Shadow

2. Stormy

3. Evening Sky

Since you're running shadow, you'll want to play hot-potato with your team when it comes to the golems. That is, when the golem is around 85~ mana (one turn from max) and your slot 1 pet has the other debuff from the golem... swap who is in slot 1, get the exploding shards debuff on them, then swap back.
When the two debuffs are combined exploding shards does massive damage, compared with a much smaller amount of one-or-the-other. You can also use divine balance in this turn so a ko'd pet is revived if it gets knocked out in the next few turns instead.

That worked very well, thank you for the advice!

I need help with this fight. Why am I dying so badly? Is it just my healer pet being too squishy to endure being in pos 1? With all the positive and neg charge shuffling it's hard to avoid.

edit: I just realized this thread says golem but I'm too tired to

you could check the woerm beating teams thread to see if there's anything that other people with the same team composition said on their experiences fighting it.
w/l/a is one of the popular element setups for the fight so there's a few (and much easier to find now I've added post links to the first post), or if you haven't seen any of the assorted guides to the fight (also linked) if one of them might help in some way another mightn't

looking at your pets, I'd say mostly you probably want to upgrade some gear (whether getting sw to +2 or higher or just getting primordial gear)
I also note that you don't seem to have the Training grounds buff active on the woerm or ent flasks on the pets- what tiers are your barracks buildings at?

I'd been trying to smack my way through to the temples for the easter eggs, I have a bought team and I'm rather behind on the grind and the barracks leveling. I was trying to learn the mechanics of the fight before I use up the few flasks I got from the event.