Spoiler tagged due to high base health and skull keys.

What the hell is that hourglass thing about?

Is it one of the rune effects? I don't recall seeing that on my game.

No clue? It was on my screen for a few minutes I feel and disappeared. I couldn't determine it being any rune effect. I think I had on the second chance, extra ammo, and infinite ammo runes at the time- which you can see I'm not dying, and I'm not above 100 armor- and that shows an infinity icon by the ammo anyways.

It's the second chance one. It is probably there to indicate that you have a second chance available and goes away after you've cheated death once. I really don't recall though because I only had that rune equipped in the last mission to upgrade it to level 2 by purposely dying in a large arena and shooting the BFG to get ten kills while in that state haha.

Oh shit. That makes sense! Thank you!