RAW/RAI - Mordenkainen's Hound Rules & Exploits

Quote from wagnarokkr >>

The Phantom Steed is a creature because it says it uses the Riding Horse stat block. None of those other things are creatures because they don’t say they’re creatures.

There’s no vague language here at all. You just want it to say something it doesn’t say.

We’re reading the same rule books.

A creature is any being in the game and it has a creature type.  But not necessarily a stat block.  (This is RAW).

Consider the following:
Conjure Celestial - Spirit from the upper planes.
Conjure Elemental - Spirit from the elemental planes.
Conjure Fey - Spirit from the Fey wild
Conjure Minor Elementals - Spirits from the elemental planes.

A spirit is a being, though it does not have a stat block here.  They probably did this for ease of use.  These are clearly Celestials, Fey, and Elementals.  The text does not call them creatures explicitly or give them stat blocks.

Likewise, I believe that a “Faithful Hound” is probably a Celestial Hound, and the opposite of a Hell Hound.  Since it is merely being summoned for 8 hours it does not fully materialize and has no stat block.

So what I am wondering is if you might use Magic Circle on any of these.  And what would the stats be if you did?  I am just thinking out loud.

The MFH is (possibly) a Celestial Hound, opposite the Hell Hound, and likely would have similar stats if it became tangible.  Just my thoughts.

Remember, there’s no actual rules for creature types (RAW).

Quote from RegentCorreon >>

Quote from packman767 >>

As for the bag of holding….. it isn’t moving when its inside because its an inter-dimensional space.  A regular bag could not move it but a bag of holding can move it relatively if you think about it.  That is the entire point of a BoH

Where are you getting this information from? It's not laid out in the description of the magic item. The bag is described as being bigger on the inside than on the outside, but not as if the contents are floating in some permanently stationary void. By default, if you pick up and move the bag then the contents would move with the bag in the same way they do for any other bag - the walls of the bag move and the stuff inside is held up and pushed along by the bag. If you placed an intangible thing in the bag then it would not be pushed by the bag's wall when you carried the bag away - it would phase through.

Another option is that the bag's interior is on another plane. That would put it outside of the MFH range limit.

An interpretation where the bag's interior is both stationary and always in range and very far-fetched. 

You seem determined to make MFH an exploitable super solution for this terrasque scenario, and you then seem to be shaping your interpretation of all sorts of other rules to align with the intended exploit - and also dismissing any and all feedback you are receiving here that contradicts the idea.

The spell is just a spell that does the things it says it does. It isn't some enigma waiting to be discovered and interpreted into a nuclear-level weapon. 

 Well the bag is an interdimensional space and has enough air for 10 minutes for breathing creatures.  Which means creatures can go into it.  We know it is an interdimensional space because of the text of the other items it mentions… read the other items description.  We know that a player can reach in and out of the interdimensional space without severing an arm, and that items can be both inside and outside of it as they transition.  Creatures, likewise.  You aren’t misty stepping into it right?

So, it follows…. An MFH can be within the bag.  If the bag is destroyed they are scattered across the astral plane.  It does not simply float through.  The bag opening is a portal, and the interdimensional space itself is merely accessed.  I propose that a player or a mfh can be within range of the other through portal of the bag no matter where the bag goes.

As for your final sentence……. Your words, not mine.  The scrolls are probably worth 500-1000 gp each.  20 mfh scrolls could cost 20k gold.  But it might simply make sense by level 20 to save a city.

There is no limit to how many hounds you can create beyond spell slots and scrolls.  They can’t die.  They last 8 hours.  They can be moved via magic action.  They can stack.  All facts agreed upon. Metamagic improves them.

I am simply making the case that they might also work on vehicles, might work with TFD, and might be a bag of holding exploit, whether or not they are creatures, which they are by loose definition if not explicitly.

And I’m applying it all toward a Tarrasque battle….. what great fun we are having!