Ashes has the spores, which also can be upgraded with the toxic growth field upgrade so for a higher chance for a better reward
Astra has the crystals, which out of all 4 loot mechanics, this one feels the more lazier and less unique because it has been already used in other maps
Paradox has the pods that have to be filled with souls in order to get the loot, i like how they use them also in order to get one piece of the wonder weapon and that also can give you very good rewards
And probably my favorite, Totenreich has the fishing mechanic which gives you also very good rewards and you can get the viking helmet in order to get even better rewards, i like how this mechanic works and that you can also lose your fishing rod if you are not paying attention