General questions and discussions.

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Regarding the Guild of Mages, here's a textual description from the currently unfinished documentation:
— On the Guild of Mages screen, you can research spells, changing the spells available in the slots.
— The research cost is (2 * spell level) mercury, sulfur, crystals, and gems, plus 1000 gold. Research in each city can be conducted no more than once a day (regardless of building construction).
— When researching, the old spell disappears from the slot, and one of two new spells is offered to choose from (at level 5, one new spell is generated without a choice). Research can be conducted multiple times in the same slot, but intermediate spells cannot be learned by heroes. Each time, the spell is generated according to the standard chances for the city, but spells that have already been in the Guild of Mages cannot be generated a second time until there are none left that haven't been.
— At any time, you can end the research in a slot for free. In this case, the current spell will become available for learning, but you will no longer be able to change the spell in that slot.
— Only one research can be in progress in a city at any given time; before starting research in another slot, the current one must be completed.

Note that upgrading to 5 Guild of Mages is not required for research.

For levels 4 and 5, the difference from the SoD version in terms of resource cost and time is not significant – only intermediate spells cannot be learned.

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A few more words about the templates.
— On the mirror templates, Kirr, Gunnar, Dessa, Luna, and Jeremy are completely banned (as mentioned above).
— On Anarchy, cartographers and other objects that reduce the value of scrolls are allowed, and guards may be shifted, and many objects can be stolen by flying (although not as extensively as in SoD).
— Many templates in the build have edits: some roads, etc., are defined. You can view them in the template editor; a detailed list of changes will be available later. 6lm10a corresponds to the 6lm10a(min) version. On Jebus, Galtran, guards, and villages of all cities are allowed.
— The template folder is now HotA_RmgTemplates. To add a new template, you need to place it there. Many templates have been removed from the default list; to restore them, simply place them in this folder.
— The old 6lm10a(min) (and similar templates) will not work correctly on this version. However, in the regular 6lm10a, the roads are defined as in the min version. It is also not difficult to recreate all other templates with roads for older versions.

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15) Something that was supposedly going to be done, but I didn't find any mention of it in the changelog:

- the ability to view the artifact pool without a hero in the city

- fixing the scouting special ability – so that it rounds to the nearest number (as in 1.4.2), and not up (as in all other similar special abilities)

This was not planned.

Goshan is available on the regular Jebus, but not on the mirror. Is this intentional or a bug?

On the mirror, both players start as Necropolises, and Goshan is only one. Therefore, he remains banned there.

A much better solution would be the ability to ban artifacts in the template editor (if this is technically feasible).

This feature has been implemented. You can ban/unban artifacts in the template. That is, if necessary, you can create a template with a Red Dragon.