Rune Trial Stones are floating structures which can be interacted with to attempt a Trial. Each trial has a different goal, time limit, and weapon. Completing a trial successfully will yield Runes, which allow further abilities to be used in combat.
They first appear in Doom (2016). They are large boulders that glow green, with a large glowing green rune on them. They also give off a loud, continual deep whispering similar to that of a Gore Nest, and likewise can be the first signal to the player that there is one nearby. After passing the trial, they crumble into a small pile of rubble with a much weaker green glow. Because they actually aid the player, it is possible that the whispering is not the same as the Gore Nest's, and may not be malicious.