With the release of TR1709 this week, the faction merger will be one of the most impactful changes to Tamriel Rebuilt since the data merge with the Project Tamriel projects (Province Cyrodiil and Skyrim: Home of the Nords) into the Tamriel_Data framework.

Like the move to Tamriel_Data, it will impact your savegame. Unlike Tamriel_Data, the filepatcher is not going to help you this time (unless you are a modder and used some of the deprecated IDs).

The new TR_Mainland will only contain the new faction assignments. All content on the mainland will continue to be optional and nothing is going to change on Vvardenfell. For additional gameplay changes, a new plugin, TR_Factions will be made available. In this first iteration, it will contain additional quests for the Telvanni Hortator questline, as well as unified faction reaction tables and adjusted rank requirements.

First of all, if you plan on starting a new game once you have TR1709 released, none of this applies to you. A new game is entirely without the unfortunate problems that carrying over a savegame always has.

For everyone who wants to keep their save game, there are several things you must do or know:

1. Your masters will change. Abot has written an excellent guide about how to progress mods with updated masters on his website. This is extremely relevant for Tamriel Rebuilt, because TR_Mainland will change internal references every time as much as a bugfix is applied.
2. Your faction progress in the mainland factions will impede your progress in the Vvardenfell ones. This is because Morrowind of course remembers what faction you progressed in, and it has applied your progress in the mainland faction to the mainland faction, no matter what any patcher has to say about it. For people like you, we included a TR_ConvertFactionProgress.esp. You will need to load this once(!) to update progress on your Vvardenfell faction. If you don‘t plan on using TR_Factions (which contains updated requirements lists for rank progression) you can skip this step.
3. Even with TR_ConvertFactionProgress.esp there are some pitfalls. Morrowind keeps certain local variables in its savegames that cannot properly be updated:
   1. While TR_Factions adjusts the reaction tables and adjusted rank requirements, these will not apply to old saved games in which script functions have been used to change faction relations (specifically the Temple, Hlaalu and Redoran during the main quest in vanilla, but potentially any other faction quests that have been added by mods).
   2. Any NPC asked about "gummidge" in Firewatch will be stuck with their old (mainland) faction.
   3. Master Mithras of Tel Aranyon, if you refused his quest, will be stuck in Mainland House Telvanni.
   4. After certain quest events, several Fighters Guild, House Telvanni, and Legion members, "Mashug gro-Dugal" in Nassudan, "Fedaves Othrendu", "Geldii", "Tenos Siratha" in Port Telvannis, and "Naleth Llarni" in Windmoth will still belong to their respective mainland factions.
   5. In a limited sense, all NPCs that are scripted to become hostile (and not through taunt or spells) will remain part of their (mainland) faction. As they are hostile anyway, this should have no impact on your gameplay.

It is our hope that by knowing these pitfalls you are able to decide ahead of time if you want to upgrade to TR1709 now, later, or start a new game entirely. While each new release of Tamriel Rebuilt contains changes, updates and bugfixes, ultimately the only one who has to deal with the troubles these cause is you.

Take care!