No loot drops at end of Delirium?

I'm confused af on the new delirium mechanic.

I see there's a bar graph. The deeper I go, the farther the little diamond moves. That makes sense.

The icons above the bar graph start grayed out, but they don't seem to change color. Although once I got the two at the very right edge to turn blue -- still don't know how.

I don't know what the icons mean. Some look like mirror shards, but overall it's just confusing.

The left edge of the bar graph starts to move towards the right -- I get this, it's the fog dissipating.

How do I "win" the mechanic in the map? I clear half the map, or most of the map, including the boss, I'm at the far right of the bar... now what? It never seems to hit a terminus except if the fog finally runs out.

When the fog does expire, nothing drops.

wtf is the secret here -- maybe being a PoE1 player has biased my understanding of what should be happening. Regardless, I'm getting almost nothing from doing a T5 deli map -- usually 1 liquid ire (the weakest one).