I am away from my books at the moment, but if I recall correctly, enchanted items with powerful effects undergo Warping. Like Longevity Potions.
Has anyone made an analysis of the typical progress of an item's Warping?
Basically, how long can an enchanted item last before it has gained so much Warping it is no longer recognisable?
Or more specifically, what happens to an old Mercere Portal?
ArM 5, p. 167, second sidebar, Warping and Non-Humans; "Other mundane creatures and things are also warped by mystical effects." It goes on to say that the rules for humans give an idea of the effect on creatures and things. Creatures with Magic Might are not affected by warping.
That's probably a crucial distinction. A Hermes' Portal is a Ritual spell; a place under that spell year after year should warp. A Mercere Portal is an enchanted device (HOH TL pp. 100-101). An enchanted device is probably not subject to warping; it is essentially the object designed to hold the spell.
However, the place associated with the Mercere Portal may be. That is, the Mercer Portal (the door or columns or lintel gate) itself may not warp, but perhaps the room or cave or whatever it is in, does.
That said, rate of warping depends on the circumstances. The Aura will have an impact.
At (picking a rate) 2 points per year, Warping Score of 5 takes about 38 years. At Warping Score 6 or more takes 53 or so years. At Scores of 1 and 3 the thing gains a Flaw, at 5 a Virtue, and at 6 and every Score point thereafter, a new Flaw.
So, I suppose the question is, at what number of Flaws is a thing warped beyond tolerance? Do things Twilight? Do they turn into Aura tethers? (I suspect this is addressed in RoP:M, but it's late and I am tired.)
I think you are right, RoP:M haves the answer: Magic Things!
I'm a big fan of Magic Things. There are quite few of them around, except for elementals, and they can make quite interesting... er... things.
RoP:M indeed says that things can become Magic Things for some reasons; it explicitly mentions being exposed to the Magic Realm or being involved in large magical catastrophes, but I'd say being continually under the exposure of a high level Hermetic effect could also quality. Which is good, because you can't put virtues or flaws into a common thing (imagine a chair with the No Sense of Direction flaw: how would it be different from any other chair?), but you can assign them to Magic Things (i.e., a Mercere Portal with the No Sense of Direction flaw can actually do pretty odd things, like making you arrive facing in a different direction). Also you can get them powers that could fit the concept, like developing glitches who trap travelers in a Regio, or granting them for a time one of its flaws (...like let's say No Sense of Direction) after using the portal.
Now I HAVE to create such a NPC: the Twisted Grumpy Mercere Portal.
Those sneaky Magi, each holding her secrets for herself. What a bunch of nerds.
PS : seeing the cost of such a ritual, I houseruled for my troup that Mercere Magi are able to kick the Hermes theory and build everlasting portals for the same amount of vis pawns, though it is a non-regular process and it would be making a move for the beneficiary... Which seems to be real indeed.
When I was making stuff up for my troupe early on in the career, Mercere created portals were permanent enchanted items that required a small vis-expenditure to 'activate' them. Anyone who wanted to teleport to another mercere portal would usually bring 2 vis as a gift, one to activate it and one to thank the Mercere.
I think 3rd edition ones worked that way - you cast the ritual, but each person going through has to pay 1 terram vis. 4th ed just made it a portal, and 5th ed made Hermes portal a year duration ritual and Mercere portals the permanent enchanted version.
I have always assumed, and it is the way our troupe plays, that Mercere Portal needs an activating trigger to work, rather than be on 24/7.
The Mercere Portal our troupe has found, will only work when a red light shines on the top of the arch in the shape of the Mercere symbol. Relatively easy to do with sponted magic. Then the portal will remain open for a Diameter duration. Though our portal also has a 'fault' in that it will only work when a particular star can be seen in the sky. Also, when we activate this Mercere Portal, there is a faint mirage of the other side.
My character hasn't checked if it has unlimited uses. He is currently wanting to check if it is possible to tell if an invisible character can step through the portal undetected, without disturbing the 'mirage'.
I don't know what the consensus is regarding how a Mercere Portal looks when active.