The Ent Leafshade might know what transpired when the Corsair ships came this way, but getting him to tell you about it might be challenging.
'There have been many strange happenings... of late...' the Ent rumbles. He slowly turns his head to look past the trees of the grove, and falls silent. After a long moment, he seems to realize you are still here. A long, windy sigh escapes from his mouth.
'It is most unusual... for so much to happen... to the Ents,' he murmurs, sleepily.
'I am called...' he begins, and after a time you realize that the sound rolling out among the twigs and branches of the grove, making them restless, is actually a long name spoken languidly in Old Entish.
'But you may call me Lathlum... or Leafshade...' he continues, his voice little more than a sigh.
The Ent Leafshade is at the grove of Tumbamálë.
King Elessar is inside the main hall of the keep of Lond Cirion, and should hear what you learned from Leafshade.