That's what I'm saying though... I use whisperweed like it's crack until I get the eldritch epiphany and still never seen more than 1 guardian spawn. I'm kinda impressed.
I ... kinda ... threw several mana pools worth of mana at the whisperweed and idled next to it. My permanent warp goes up to the end of the first golden part of the meter ... and my sticky warp filled almost all of the rest of the meter ... the temporary warp was off the charts and would have probably filled another bar by itself. I also went in two outer lands mazes ... the first one took me maybe two hours to finish and I farmed a bit in there for eldritch eyes.
A friend of mine also reported getting swamped with 3-guardian spawns now and then, playing on Agrarian Skies 2 ... and I know for a fact he is not as laissez faire with warp as I am, so it appears that just a full warp meter and broken brain icon is enough for the nasty stuff.
Come to think of it, I think I used the whisperweed far past the second ephiphany. I keep forgetting there is no third ephiphany and getting the last part of the eldritch tab takes scanning the primordial pearl instead. That might explain why you haven't seen harsher warp events.
I haven't tried the diabolist fork on one of those yet, but I'll keep it in my hotbar and report back once I got another spawn. spawns went back to single numbers after I used the spa recently.
Also concerning advanced reservoirs: I love them. it may cost more ressources, but I like these reservoirs on an aesthetical level ... also their sound. Creeking void metal everywhere! I currently have 12 connected to my advanced furnace ... one side is getting a bit clogged, mostly terra essentia. So I thought I'd start some terra farming, then noticed nothing there actually uses terra essentia, only terra vis. So I'll have to use alchemy or infusions to get rid of that ... or, what I also thought off, was to add an alchemy golem, a reservoir in the ground, pipes going off of that into a second room below the advanced furnace room, add a directional pipe to it, so that essentia only can be pumped towards it, not out of it ... and then maybe use, directly behind the direcitonal tube several filtered tubes to selectively feed certain essentia types right into crystallizers.
After that I'll prepare another 64 advanced reservoirs. Just made the essentia buffers and warded jars for that already. Just need to throw enough ender pearls and cracked sand at my advanced furnace to get enough essentia for the two stacks of void metal.
Sure, the advanced reservoirs can clog fast ... but if you select the items to melt down a bit more carefully, that could be avoided. I made the mistake to use leather for tutamen for example and am clogged a bit with pannus ... now I just use iron leggins (bes tratio of tutamen to iron used) and drain the excess metallum via adding a stack of 64 iron nuggets to my alchemical furnace.
For vacuous I use glass phials ... alienis and tenebrae are a bit harder to get pure sources for. I use ender pearls and cracked sand, as I already mentioned somewhere in this text wall. So that means an excess of iter, perditio and terra. perditio is easy to get out of the system, just add a stack of cobblestone to get sand. Eats 192 perditio for a stack of cobble.
Not sure what to use to get rid of iter yet, but once I expand my system and add the filtered tubes and a handful of crystalizers, I won't have to bother too much with thinking of creative ways to get rid of the essentia without crystalizing it.
Edit: Oh and I was also constantly wearing the void armor(couple days of real time), so that's ... warp 6 I believe. Plus the warp 2 from the primordial crusher that I used a little bit. Which means that my temporal warp didn't naturally decrease as time went on.
Edit #2: I just managed to get an imprint for eldritch guardians. So it definitely works. Also just looked at NEi and it seems that nearly everything can be imprinted. What doesn't work is imprinting bosses or anything from the pech family except the forager.
