Whilst soloing a reive in Yahse, I thought someone else must have joined me when I noticed that I had haste.
Didn't see anyone at all, so I thought maybe it was a Rieve momentum bonus.
Then I did the 'Maat' fight, popped Valliance (stupidly buffed outside, so vallation timer was down) and saw the hsate pop up again!
P.S. really easy 3k Bayld lol (at 99)