The base game portrayed the Imperials as enemies. You see: the legalization of necromancy, the Worm Cult of councilior Mannimarco, Daedric plots... As well as the silence of Imperial officials who know things are bad.
For the anecdote, Abnur Tharn was originally supposed to be our enemy in the final quest of the main story. This storyline has since been scrapped and Abnur is the friend we know. Anyway, the Empire and the Legion were absolutely our enemies.
Since then, recent content has improved the image of the Imperials.
With Gold Road we go to West Weald. In the base game, Count Calantius of Skingrad decreed the annexation of the South Weald, the Arenthia Vale of Valenwood, with the ratification of the Elder council.
Colovia plays a major role in base game invasions. But it is interesting to see how corrupt these legions are.
So of course, many will say "why don't they stay at home and solve their problem? Instead of invading others?".
The excuse is war. There are certainly legions trying to reclaim the territories of Cyrodiil. Others on punitive expeditions in the territories of the alliances, which themselves are terrible among themselves.
Then there is the method. Like that of reducing conquered peoples to slavery. That and the promise of social elevation and land ownership. Notice this looks like the Romans, which is what Imperial Legion is inspired by.
Anyway. Let's return to the subject of involvement in Planemeld.
> Exemple of a Legion completely involved in Planemeld
Magus general Septima Tharn's Seventh Legion. They basically have a dark reputation. Today, they could be described as war criminals.
Beyond their reputation, it is interesting to note that the Seventh Legion is openly associated with Worm Cult and involved in Planemeld.
It's simple. Among the members of the Seventh Legion, we have Daedric invocators and... Daedra.
More subtle, it is a staging: the imperial camp of Old Tower. A lieutenant and his soldiers have a celebration animation. They are oriented towards a dolmen, that of Ephesus.
> The Legion of the West Weald situation
It mainly includes Colovians who were free by birth and many peasants who are committed to the promises of land and social advancement. As Colovians, they are mainly devoted to the Eight.
The invasion campaign is an imperial decree. General Lavinia Axius was designated to lead the mission.
This Legion has no Daedric invocators or even Daedric creatures in their ranks.
The general's choice was fatal. Because Lavinia is associated with Javad Tharn, leader of Stonefire Cult.
The presence of Stonefire Cult is only known to a minority. If General Lavinia reveals the presence of this Daedric cult, she knows that her soldiers will mutiny... This is what happens in the Colovian occupation quest in Arenthia.
As for the appearance of the Dolmens, they are concentrated in areas occupied by Stonefire Cult and their army of Dro m'Athra. The Dolmen appearing in Arenthia only occurs once the Legion is repelled. The temple district is occupied by cultists.
Finally, Legion of the West Weald is clean. I have no doubt that Calantius would have had a say if he learned for Stonefire Cult.
As for the motivation for this invasion, Calantius is opportunistic and has seen that the region belonging to the Dominion south of Skingrad does not put up much resistance.
There is the situation where Skingrad is allied with the Empire. The heart of the Empire is attacked by Dominion (and the other alliances), as well as a piece of West Weald. It is a punitive expedition of conquest.
But there is also this theory... If ZOS considers that EVERYTHING happens in 2E 582, this expedition may be a response to Dawnwood's invasion of West Weald. At the time, the Imperial authorities saw Valenwood invading West Weald, and probably did not try to differentiate between Wood elf associated with Dominion or not. For them, it remains bosmer and finally "Dominion".
Legion of the West Weald returned to Colovia. There is no doubt that today they are waging their true war: resisting the assaults of Ithelia's minions.
It remains to be seen whether they were there, and what role they played, during Colovian Revolt.