Must... resist... reading that!
For Heretic, I don't see a lot of ways to set up an infinite loop.
Let me do some theorycrafting.
It takes 3 mana to build a wall, 4 to break with PISORF, or 6 with ENDISWAL. Building a wall gives you 15 CP.
If we look at this without any extras, the only way to make this infinite would be with a Gnome, to keep drinking more potions to build more walls. However, you would have to build 6 walls per potion - you also have to destroy those walls to have piety to lose, so that means you need to spend 7*6 = 42 mana. Even with the Heretic's big mana pool, there's no way you'll get more than around 8 mana per potion. So no dice.
What if we add BLUDTUPOWA to the mix? Assuming no blackspace left, and no health modifiers (to keep it simple), you can cast BLUDTUPOWA 3 times for 1 mana each. Then if we can also get a Fire Heart, that will add up to around 2 extra mana per full mana bar. Of course we can also add Dragon Soul, which should be around 3 extra mana per full mana bar. And if we add Rock Heart, that boosts both sources of mana - Rock Heart is probably the best single item here as it adds up to 5 mana (4 from walls, 1 from BLUDTOPOWA) per full mana bar.
However, I think that's it - I don't see any other ways to help your mana spending here, so I think this idea is dead.
On the other hand, I think something like this COULD work. A sample strategy:
Go VGT Gnome Heretic, prep Binlor and Rock Heart or Dragon Soul (we scum for the other one).
Then we want the Golden Statue in the first tower. If we prep DR, it won't hurt us at all when we strike it.
All we need now is the Knockback boon from Binlor (can't prep Bear Mace because we need the Shield for DR). Once we have that, (and also found IMAWAL through scumming) we can now farm Binlor piety at the cost of 3 mana per 15 CP. This is a more managable 18 mana per mana potion, which coupled with BLUDTOPOWA, Rock Heart, and Dragon Soul may actually turn a net positive in mana, allowing us to actually pull of an infinite amount of conversions (and note that since the Golden Statue weakens us, we'll end up dealing only 1 damage to it per hit - since it is level 8, it will regenerate at an insanely fast rate, allowing us to do this practically forever).
This probably isn't actually worth trying - there's so much scumming involved, and unlike the Infinimuter, you're basically just permanently relying on the Dragon Soul cooperating, because if it doesn't, I think you still don't turn a profit on mana... it's an interesting thought, though.