They don't eat, they don't sleep, they only require gold. This one at the screenshot probably missed the payday or something, I can't think of any other reason for him to be unhappy. The spell which gives gold to a creature is not effective, his mood is still unhappy. So that's it, there is nothing players can do to make them content again.
It makes them happy to some extent as any other unit but it might not be enough to recover fully.
The reason for this, is that the happiness provided by the spell depends on the wage of a minion, which normally makes sense.
The higher the wage, the less the gild spell effects the happiness and sentinels have an outrageous high wage.
So to make them happy you'd need to apply the spell like 100 times.
And there lies the mechanical issue.
There would be multiple possible solutions, eg. we could just make an exception for gold units, so they get much happier by the spell or it does not scale by the wage for them or it make them instant ecstatic or any other solution.
But I would like to get confirmation from the designer, which solution we should apply best.
Josh Bishop How do we deal with this mechanics issue? Any idea?
I suspect he was busy killing heroes coming from the gates at north. Even so, I spammed the gold spell at him, he has 4000 gold atm with 2400 wage (he had 0 gold), and he's in the middle of a treasure room if it's not enough for him. No more reasons to be unhappy.
The man truly knows how to hold a grudge it seems. ;)
Had a look into this and can confirm. It appears that these units do not have any need other than gold. This means if they ever miss a payday or for whatever reason get less wage than necessary they will drop immediately to unhappy.
Not sure why giving them the pay after didn't work though or why they missed the payday in the first place. Exporting to Internal Tracker :)
Alright we came to a conclusion.
All units but Sentinels got happy enough by Gild, because their wage is in a normal range.
But Sentinels (or more generic gold units) were not too overwhelmed by the gold amount given by Gild (because it is not much in contrast to their outrageous wage).
Thus we added an extra flat happiness bonus for Sentinels(gold units), which does NOT scale with the wage.
Depending on how unhappy the Sentinel already is, one cast of Gild might not be enough to recover, but it will definitely have now a remarkably positive effect on their happiness.
TL;DR.
In next patch Gild will make Sentinels way more happy.