On brand wheels, there is a mastery available that reads "Recover 10% of mana when a brand expires while attached". In theory, if we reduce the brand duration low enough, we can proc this effect frequently enough to sustain the monstrous mana costs of Indigon or Archmage. And since we are recovering by a percentage of maximum mana, we don't really need to invest much into mana regeneration. Our mana recovery will basically scale with our maximum mana.

Reducing Brand Duration

• So this is actually the easy part. Wintertide Brand is the shortest duration brand at a base duration of 2 seconds. With Swiftbrand, 21/20 Less Duration, and the Window of Opportunity wheel and the Less Duration Mastery, we get a 90.31% less duration. This brings our brand duration down to 0.198s. Therefore, we can get 10% of our mana roughly every 0.2s.

• There are more options to reduce duration even further if needed, but most likely overkill. Swift Affliction gives us another 25% less, and Timeclasp and Warped Timepiece are also options.

• Penance Brand is the next shortest brand, which would last for 0.264 seconds in this same setup.

• The "Remarkable" cluster jewel notable gives a 30% chance to cast an additional brand. Stacking 3 of these notables would give a 100% chance to cast 2 brands at a time, potentially doubling our mana gain, but I'm not convinced the opportunity cost is worth it.

Automating Brand Placements

Now this is the tricky part. We've established that we can bring our brand durations sufficiently low, but how do we actually place brands fast enough in the first place? Turns out we have a few options for this.

Cast while Channeling

Perhaps the weakest option out of all the others. We are stuck with a 0.35s trigger rate that can't be scaled by CDR, and our brands have quite a few support gems so we'll need a 5-link at minimum. Doesn't seem worth the opportunity cost, but it is an option.

Using Cast on Crit to trigger the brands also doesn't seem worth it for similar reasons.

Cast when Damage Taken

If we setup a loop where we can damage ourselves, we can use Cwdt to trigger the brand automatically. We can use a lvl 1 Cwdt and just keep our brands at lvl 1 as well. Note that we can still use a 21/20 Less Duration support as it is a support gem.

Cwdt has a 0.25s cooldown and can be scaled to trigger more frequently with CDR.

There might be some very interesting things we can do with Scold's Bridle + Archmage and Olroth's for a pseudo wardloop setup. Best options otherwise would be Storm Secret or Eye of Innocence if you can satisfy their conditions.

Kitava's Thirst

Kitava's Thirst has a 50% chance to trigger all socketed spells when you spend 100 mana to use or trigger a skill, with a 0.1 second cooldown. Archmage easily lets each cast of our main spells to reach that threshold. We can socket multiple brands in Kitava's as well, something like Winetertide/Penance/Swiftbrand/Less Duration. Provided we have Runebinder, this would almost double our mana recovery.

In theory, this might be the best option. However, it competes with Indigon so we can realistically only use this on Archmage setups.

Mjolner/Poet's Pen

Both these weapons have a 0.25s cooldown. Penance Brand would be the shortest brand for Mjolner.

Cospri's Malice

I put Cospri's separately since I think its the best option out of all the triggerable weapons. We can simply socket Wintertide/SB/LD in it and use Archmage on our main CoC setup. If using Archmage, we can have up to 4 more spells in Kitava's thirst to automate some multi-button builds.

Build Concepts and POBs

I will start by putting a disclaimer that these PoBs are incomplete and just a rough draft of the ideas. They are not functioning builds.

CoC Archmage Ball Lightning Inquisitor

https://pobb.in/Ggvh2kj3ihGw

We use Ball Lightning with Archmage in a CoC Cyclone setup. We use a double brand setup, both of which are triggered by Kitava's Thirst, for double the mana recovery.

Indigon Battlemage's Cry Smite Inquisitor

https://pobb.in/3w6sp71bJSjL

We scale increased spell damage by spending mana through Indigon. We convert this into attack damage using Battlemage's Cry. Anomalous Mana Leech gives us 0.5% increased damage per 200 mana spent recently, and this translates into a ridiculous bonus considering how much mana we are spending. We can scale this even harder by going with Dialla's Malefaction to scale its quality. We use Herald of Thunder and Storm Secret to trigger the brand on Cwdt.

Closing Notes and Thoughts

• If you are planning on theorycrafting with Indigon, I highly recommend reading this post by u/agentyoda on indefinitely sustaining Indigon.

• I am currently trying to POB a wardloop setup with Archmage and Scold's Bridle to see if we can set up an infinite loop.

• Cast while Channeling for the brands might be viable on Stormbind, but I'm not too familiar with Stormbind's mechanics.

If you've made it this far, thanks for reading! Hopefully the information here gives you some ideas to create some wacky builds.