#Preamble

Botania is a pretty good Minecraft mod that I've once again been playing recently, together with some friends and other mods. Looking for a way to sustainably generate decent amounts of Mana without too much setup, the Thermalily caught my eye. In short, it generates Mana by consuming Lava source blocks. However, this comes with a catch: There's a cooldown; And if you let it eat another Lava block before the cooldown has fully ran out, it resets entirely, generating no mana. Additionally, the cooldown is random and between 20 and 300 seconds.

One would be lead to believe that timing the feeding periods is a simple matter of checking whether the comparator output of the flower has reached 0. Unfortunately, the comparator never actually updates how much time is left! You get the indication of how long the total cooldown period lasts and have to do the counting yourself.

In more technical detail, whenever the Thermalily consumes a block of Lava, it will steadily generate Mana for 45 seconds. After this, a random integer, $N$, between 1 and 15 is rolled. This number is the strength of the comparator's output signal, and the cooldown period will be $N\times 20$ seconds.

This design uses Mana and Artifice as well as Immersive Engineering for the infinite lava source and transportation of it respectively. However, at its core it does not depend on any mods outside of Botania. You may have to get creative to design an alternative infinite lava source including transportation, but this should be entirely possible in vanilla Minecraft. Alternatively, there should be plenty of other mods with easy liquid transport and/or infinite lava sources. Once you have designed the alternatives, replacing the existing methods should be as simple as plugging the old ones out and the new ones in. You won't have to mess with the redstone.

#The Design

This is the whole design. Let me break it down for you .

#Thermalily

Sitting on the piece of green wool, the Floating Thermalily absorbs any lava blocks in a 3x3 area centered at its position, but only at its own height. There will never be any lava surrounding it in its default position. Once the cooldown is up, it will get pulled back by the sticky piston connected to it for a few ticks to absorb the lava behind it.

#Hex Memory

On the yellow wool, we store away the output of the Thermalily's comparator so we can decrease it gradually. The signal strength stored will only change if the comparator in subtraction mode receives an input from the left, or if the comparator that's reading from the Thermalily gets unlocked. The former happens once every 20 seconds, when the clock triggers. The latter only happens when the currently stored signal strength is 0 (so the cooldown has run out) and the clock triggers.

Upon reaching 0, the piston will be triggered.

#Clock

The light blue wool path reads a redstone signal from a comparator connected to a Hovering Hourglass from Botania. The hourglass contains precisely 20 regular sand blocks. This will make it turn, and in the process emit a redstone pulse, exactly every 20 seconds.

We use this for two things: unlocking the thermalily's comparator and subtracting from the stored cooldown. For the former, make sure the repeater visible in the bottom right of the image is in fact set to 2 ticks. Otherwise, some weird comparator shenanigans that I only half understand may ensue.

To reduce the cooldown, we need a pulse with a signal strength of exactly 1 to reach the yellow subtract-mode comparator. This is why that repeater facing into the block is there. The signal with strength 15 is passed to the subtracting comparator on the opposite side, which has a barrel next to it. This barrel contains exactly 24 non-stackable items, giving its comparator an output strength of 13. The subtracting comparator will output a signal strength of 15-13=2, which gets reduced by 1 more due to the length of the line.

#Piston

The piston logic is contained on the orange line. Please note the unfortunately barely visible redstone dust on the very right, facing into the wool block that ultimately triggers the piston. By default the piston is extended, only quickly retracting for a handful of ticks when the countdown runs out. To limit the retraction length, I use an OR-gate off-pulse limiter from the Minecraft Wiki. Note once again the delay on the bottom repeater.

#Lava

For the lava source, I use an Urn of the Molten Core¹, which is a 1-block infinite lava source.

For transport, I am using a Fluid Pump² from Immersive Engineering. Fluid Pumps require a negligible amount of RF , so for that I'm using a Mana Fluxfield which is getting fed by a Mana Spreader located right under the final Mana Pool. Next to the Fluxfield is an LV Accumulator with an LV Connector on top. The connector is then wired to the connector atop the Fluid Pump using an LV Wire. Note that you need to use an Engineer's Hammer to set energy input and output sides of the Accumulator. Fluid Pumps also require a redstone signal at the base, which is why that redstone torch is there.

Next, I transport the lava to a Fluid Outlet using some pipes. Be very careful here to use an Engineer's Hammer to set all sides except the bottom to No Connection, only then declare the side facing the pipe as Fluid Input. Also beware that placed lava will tear through pipes, so don't use those as walls. Additionally, the Fluid Outlet gets disabled if powered by redstone, so it can't be next to that orange block.

#Mana Transport

During their 45 seconds of production time, Thermalilies produce Mana very quickly. Getting this Mana into a pool quicker than it is produced is a bit of a challenge. Dedicating the Thermalily its own buffer pool placed directly in front of its own Mana Spreader lets said spreader output the Mana quicker than it is generated.

To then transport the Mana from that buffer to the final Mana Pool, I use an Elven Mana Spreader with a Combined Potency Velocity Lense. This keeps up with the average output of the Therma Lily.

#Stacking

This design was made with very easy stacking in mind! Here are some notes on how to stack optimally.

You will only ever need a singular hourglass.

#Mirroring Horizontally

When mirroring the design horizontally, you'll notice that you don't need another barrel.

#Stacking Forwards

To add another module forwards just extend the clock line with a redstone dust and repeater. You can continue doing this indefinitely so long as you can make your Mana Spreaders reach.

#Stacking Up

Just extend the staircase 👍

To have Mana Spreaders in the back connect, I reroute them to the sides.

Note that there is no second Elven Mana Spreader added on the Mana Pools because one can handle both it's connected to.

#Mirroring On The Other Axis

Raise the stairs and extend the build into the opposite direction. You might have to get creative with Mana Spreader wiring.

#Addendum

Of course when deciding to use Thermalilies I first took to my favorite search engine. To my surprise and frustration, all the existing designs and responses had people just waiting the maximum possible time of 5 minutes and 45 seconds. While at first I had assumed everyone was just too lazy to put effort into roughly doubling their output, it turns out the variable cooldowns were only introduced in May of 2023 with version 439.

The efficiency was calculated using the following method, where $160$ is the average number of seconds a cooldown period lasts for: $$E_{\mathrm{ideal}}=160+45$$ $$E_{\mathrm{current}}=160+45+15$$ $$p=\frac{E_{\mathrm{ideal}}}{E_{\mathrm{current}}}=0.931818=\mathrm{93.18\%}$$ As you can see, the place where we lose efficiency are the 15 seconds we lose between cycles due to our 20 second interval alignment. It's probably possible to achieve >99% efficiency using 5 second intervals and counter multipliers or something, but I didn't feel like putting in more effort. I'd love a message if you manage to improve the design so I can link to it here :)

Finally, massive thanks to one very kind user on mattbatwings' Discord server, without whom I would not have gotten this far!