I like all the words being there, but maybe for realsies the wording could be shortened a lot?

Fortitude (Enters play with a totem aura)
Fortitude (Can regenerate once)

I definitely didn't get that the ability is a property of the Aura token itself, and I still don't get that from reading the reminder text. So the Aura would be what it is and if it was moved to some creature without fortitude, it would still work fine... right?

My suggestion for that would be:

Fortitude (This [creature] enters [the battlefield] enchanted by a/an [colorless] Aura token with "If enchanted permanent would be destroyed, instead remove all damage from it and destroy this Aura.")

No, Tahazzar is right, it's ambiguous. With the wording the way it is, I couldn't tell you what happens when the aura is moved, since I can't tell if the ability is attached to the aura or to the creature with the Fortitude mechanic. My best guess, as written, is that the aura 'shuts off' if it isn't on a permanent with Fortitude.

I would suggest "An aura token with the ability 'If enchanted permanent would be destroyed...'"

It's also possible that this card, if printed, would include the words "...enters the battlefield with an Aura token attached to it with the ability 'Enchant creature. If enchanted..." But since reminder text doesn't technically need to include everything, maybe Wizards would do what you did too, and shorthand how auras work.

I also find it funny to think that this could be a dreaded nesting mechanic inside a mechanic if you wrote it that way. "...Aura token with the ability totem armor.'" I wouldn't suggest that. But if I was in development and this floated in front of me, I'd question why we needed the Fortitude keyword when we could just make a bunch of creatures that put Totem Armor tokens on permanents. We wouldn't even need to restrict that to enter the battlefield effects.

You know, sometimes I come off as being critical when all I'm trying to do is be helpful. Sorry. This is a good mechanic. I'm just trying to lay out options.

So 'divine armor' from heartstone? I've seen this being suggested plenty of times - usually they tend to use some kind of a counter. I could see some kind of a token being slightly better.

Yeah, among other things. I'm also inspired by Palladia-Mors, the Ruiner etc. But the base idea was answering the question: "What's an Aura that is so simple that it could be used as a token, but not interchangable with a +1/+1 or -1/-1 counter?"

And I came up with the same answer as WotC: an enchant ability and totem armor.

This does some raise some questions though. What I get here is that the effect is tied to that specific Aura. What if an Aura token was moved from another fortitude dude to this? Would it been able to survive three hits before dying since it has two Auras? Or is the second moved Aura token ignored by the fortitude ability?

I don't know how you can "get [...] that the effect is tied to that specific Aura" and still have those questions. The effect is tied to the Aura token created by the ability. If another Aura token is moved to this that Aura token has whatever effect the ability creating that token has granted it i. e. if it's also a token created by toughness, then yes, this will work exactly like two Auras with totem armor are supposed to work.

... Wait, hold on a moment. Does that 'enchanted permanent' refer to any permanent that's enchanted? Like, if some other dude was Mind Controlled and were to die, this would destroy the Aura instead..? That wording is ambiguous if you ask me.

No, "enchanted permanent" refers to the permanent that is enchanted by that specific Aura - it's the exact same wording totem armor and Pacifism use. Pacifism does not stop all creatures that are enchanted from attacking and blocking.

The wording you are thinking about is used on e. g. the Magemark cycle (e. g. Beastmaster's Magemark). If I wanted that I would use "any permanent that is enchanted" rather than "enchanted permanent".

If you think this wording is ambiguous, then you must think the wording of every single Aura is ambiguous. The very least this would need to say to even remotely imply your reading would be "an enchanted permanent" which would mean there could be multiples - the current wording is an established MtG-template refering to the single well-defined object an Aura is attached to.

So 'divine armor' from heartstone? I've seen this being suggested plenty of times - usually they tend to use some kind of a counter. I could see some kind of a token being slightly better.

This does some raise some questions though. What I get here is that the effect is tied to that specific Aura. What if an Aura token was moved from another fortitude dude to this? Would it been able to survive three hits before dying since it has two Auras? Or is the second moved Aura token ignored by the fortitude ability?

... Wait, hold on a moment. Does that 'enchanted permanent' refer to any permanent that's enchanted? Like, if some other dude was Mind Controlled and were to die, this would destroy the Aura instead..? That wording is ambiguous if you ask me.

Certainly. That's part of the appeal.

My idea is that the bonus itself is something that does still require an investment by being an activated ability (rather than the static boni we see usually) and is only useful in solving situations rather than increasing the threat level of this card.

And obviously it's a extremely flavorful line of text, so the real question is only: How much would this ability cost?

Kind of busted to make a legendary lieutenant

See Vhati il-Dal, Repentance as well as Abandon Hope/Broken Fall.

See also Angelic Field Marshal, Bastion Protector.

This is as much Vhati as I could make the card possibly, right?

Yeah, Law originally was introduced for rule setting enchantments like the one you mentioned. The issue with using artifact tokens is that I feel it violates the distinction between enchantment and artifact. Artifact tokens get to be Equipments, Vehicles and stuff that taps to activate abilities in my book, Clues get grandfathered in.

But this effect clearly is a reference to existing enchantments, so I'm going to have to figure out what kind of magic Hieromancer's Cage is - maybe it justifies a new enchantment type, but I'd prefer a shorter term for it than "Imprisonment". Maybe "Arrest"?

A very good one if not already in use actually would be the mechanically distinct "Seal" for Seal of Fire etc.

Is this like an ETB ability or..? Flavor wise this doesn't really jell IMO. How are the laws themselves banishing the creature? I would imagine cards with the type 'law' would be more like Rule of Law. Ie. global effects. For this particular card I could see artifact enchantment 'Shackle' tokens - or something to that effect.