Vines at Fort Trinity
That’s a topic that would fit best in the Lore section of the forum.
Nonetheless; I do agree that there wasn’t particularly any reason why these were here in the first place, which would add to WoodenPotatoes’ theory about Pale Tree Corruption (Basically, the Pale Tree is spreading its “corruption” just to “override” the existing corruption so that it can’t be corrupted anymore [/tinfoilhat])
You refer to the ones on top of the Pact fences with the blue glow?
They’re part of the anti-risen defenses that mixes sylvari magic, asuran magitech and the Blue Orb’s power, the latter seems to be fueling the Alseta Generator – the system was, in part, designed by Arcanist Slizz who is found within one of the Orrian jumping puzzles. The Blue Orb is part of the Personal Story plot.
It has nothing to do with Mordremoth – who was still sleeping at the time – beyond the indirect connection of the sylvari presence.
It’s one of the many “hidden lores” of the game.
Stop treating GW2 as a single story. Each Season and expansion should be their own story.