incredibly valuable? maybe i missed something but but if the normal passives weren't buffed with the decay update, they need to be 10 times as potent to be mildly valuable in early game, assuming you find 6-7 of them (and i believe they are just as weak as their decaying friends)
But they never stop running, never decay. On a server, plant a chunk loader next to them and have unlimited free mana. It's slow, but that doesn't really mater. Early game, you have a completely free source of mana, no infrastructure needed. That can give you enough generation to work with, running some of the early botania items for nothing. It isn't much mana gen, so you will want to move on from them, but they are good enough that if you find them they are worth building near.