This message is mainly directed to Foucter, who may or may not be lurking this forum.

I have managed to reach Level 28, and found three Ruby Power Node(s):

- one in the North-West, in a room full of barrels, where the RPN dropped after blowing up a nest
- one in the North-East, after solving a 'focus rod'/'extractor machine' puzzle
- one in the South-East, in a room with nests, where the RPN dropped after shooting a discoloured wall crystal

But I cannot find the fourth RPN. I have pixel hunted every 'room' in D28, shot every wall crystal and every rock, and found nothing. I have cast Detection and scanned the map, and found nothing. I have replayed the level from an earlier save, and nothing different happened. I have exhausted all avenues of progress, and am completely stuck.

For what it's worth, I've already found all the Amethyst and Sapphire Power Nodes, and I'm pretty sure this is the very last puzzle before the end-game sequence. I've spent over a decade (intermittently, of course!) trying to beat this custom quest, and I can almost taste victory. One final push, and all that.