How big is Dragotha's phylactery? How much does it weigh? In The Library of Last Resort it's described as "a large package, a strange container with its sides carved in the shapes of leering demonic and draconic faces" - but how big is a large package? The illustration in Kings of the Rift matches that description, but has no sense of scale. Here, it's described as "a ruby-red box, its faces carved with leering dragons" that floats within the ribcage of a dragon statue. It's clear from the stats provided that it's not a standard Tiny lich's phylactery, and it's implied that a Large humanoid would be able to pick it up and carry it away, but that's about all there is to go on.
Well, it should prooobably be small enough for the PCs to be able to carry around.
I can't find it in the adventures anywhere, but I'm pretty certain I either read or decided when I ran this that the phylactery was about two feet tall and 40 lbs. Big enough that they can't just tuck it in their (non-magical) pockets, but small enough that one person can carry it, if awkwardly.
Yes, I had the ark of the covenant image in my mind when I first read that scene in The Library of Last Resort, too! I imagined the druids carrying it on some sort of wooden frame. However, elements in Kings of the Rift seem to suggest it's smaller than that - floating in the dragon statue's ribcage, and a single humanoid creature being able to make off with it. I then went back and re-read the scene in The Library of Last Resort and realised that nothing in the description actually gives you its size, or suggests that all the druids are needed to carry it - hence my original post.