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When the 3DO console was around, there was a need for some kind of "Chronicles" and other games that could be installed on top of them. Now, they only exist as campaigns for Platinum, SoD, etc.
In general, Van Caneghem shouldn't have made the "Chronicles" part of the official M&M storyline, adding Tarnum and Verzhak to HoMM4. The merging of the Barbarians from former Antagarich in HoMM4 could have been done by someone else. They could have created a character-"helper" for him (like Tarnum in the storyline of HoMM4 in relation to Verzhak). And the reason for the destruction of Enroth could have remained connected to the Ice Blade. Perhaps Van Caneghem did this because the "Chronicles" were a creation of 3DO. In general, the "Chronicles" don't really fill in that many "gaps" in the history. These attempts to fill gaps sometimes feel like "reinventing the wheel," as everything is already well explained in M&M6-8 and HoMM1-3 with the add-ons. In some places, the "Chronicles" create an atypical need for M&M to "seriously elaborate" (the Underworld in the corresponding "Chronicles"), and sometimes even create inconsistencies (the World Tree) and create some ambiguity in the chronology of Enroth (the Brackadune Empire and the Jarg Horde, Tarnum's war with Brackadune, the liberation of Tatalia) (although this isn't that serious, but the presence of such moments is undesirable) and not only that (the ancient Barbarians of Antagarich - the Ancestors). Also, in the "Chronicles," this absolutely unnecessary "breaking of stereotypes" began, which continued in HoMM4. I'm talking about Gavin Magnus, who in M&M7 (where players first see him in this NWC product) was a mage of athletic build, with the face of a mature man and a black beard, but in the "Chronicles," he is presented as a young man (of course, I understand, he's immortal, he shaved his beard, etc., but why was it necessary to change this?). In general, it seems to me that the gaps are truly filled in only in "Clash of Heroes" (what happened to Mutara before the Reckoning) and in "Armageddon's Blade" (how the Krigane learned about Enroth, although this could have been done without, but the plot there is interesting). You can't really criticize the plot of "Armageddon's Blade" (if you abstract away from the previous part - the World Tree), "Clash of Heroes" (it was a mistake to place its time period "by release date," like the other parts (this terminology worked well and didn't conflict with the history), which significantly changed the time period of "Clash of Heroes," although he told me that he would reconsider this issue) and "Ice Blade" (the reason for Kilgore acquiring the Ice Blade on the Isle of Thieves, and therefore the Reckoning, shown in the opening cutscene of Heroes 4, could have been invented and "incidentally" mentioned in HoMM4, as well as the facts about the conflict between Jhel and Kilgore, but the plot doesn't conflict with the history). "Rebellion," which tells about the founding of Tatalia, also doesn't particularly conflict with the plot, although it creates a small conflict (there are no disagreements between Erathia and Tatalia due to the long-standing "oppression of the swamp dwellers" in M&M), but even without this "liberation of the swamp dwellers," it could have been done without. "Armageddon's Blade" has the best plot, IMHO.
In general, it would have been quite possible to remove the "Chronicles" from the canon of the M&M universe. The main characters of the "Heroes 4" campaign, "The Gathering," (the Barbarians) could have been a stepfather and son, uniting the Barbarians in the Lands of Tribes, but not connected to the "Chronicles." Mentioning Kilgore's war "with the rest of the world," it could be mentioned that he obtained the "legendary Ice Blade, the enemy of the Blade of Armageddon" on the Isle of Thieves. That's perhaps the whole short list of what would need to be changed in Heroes 4 if there were no "Chronicles." But then there wouldn't be the inconsistencies and ambiguities mentioned above. Mutara could either be completely ignored, or, if you want to get creative, come up with some reason for her non-participation (or even a scenario for her participation) in the events of the last years of Enroth before the Reckoning. It's not that important.