Found in various places (Desert, Badlands, Nether, Places like that) within a decent sized tent. It sits in front of a fire. Its head will track the player around the tent, waiting. Once within, the player can do a few things. The player can trade for some things, which change every day (In exchange for other lesser mob drops (eg, lantern goop, naga fangs), you can be trade Anything from a lesser version of its robes (which make you resistant to fire, not taking damage for the first 2 seconds of being on fire), to diamonds/emeralds/ender pearls, to scrying ash(it is craftable by other means, put a ender pearl in a furnace), and more) If attacked at this point, it will throw a orb. which causes a explosion, at the player (no terrain damage, lots of smoke, smallish amount of damage) and vanish in a puff of smoke, not to be seen again (either forever, or for a absurd amount of time (10-20 minecraft days?)).
You can also throw one of a few items into the flame. Scrying powder will create a puff of smoke. After which, the Scryer says a prediction, which will come true (kinda like the witchery crystal ball, now that I think about it.) Blaze powder, which does the same thing, except most of the neutral predictions are gone, and it is replaced by some really good predictions, and some really bad predictions, both ends of which more are extreme than the scrying one gets, bone meal, which is like scrying powder, except worse (less predictions, most neutral, some bad, almost no good, and all are less extreme), gunpowder, which is exclusively bad, and has a chance of exploding (making the scryer leave), sugar, which gives a random potion effect, and divining dust (made through smelting a eye of ender) which is even more extreme than the blaze powder, but also has some extra neutral predictions. (predictions can take anywhere from 10 seconds to a few minecraft days to take place, at random) (some of these interactions can be taken out, although most use the same framework, so it should be easy if you have one in) (other possible interactions could be the lantern jelly, nether wart, etc)
If you somehow manage to kill the scryer before he escapes, you will get his robes(with the full set when using ender pearls, a puff of smoke appears when you teleport, you get jump boost, strength, speed, temporary fire immunity, 5 hearts absorption, armor equivalent to leather otherwise), and the scryers eye, which when right clicked on a fire, will change the fire (will float above it), allowing you to have the gift of prophecy (same as normal) without the hassle of a trip into the middle of nowhere.
So, I was think about my Moonlight Guild (Mostly how I couldn't come up with anything for them), when I thought about the Fay Lizard. This thought lead to how sometimes the moon is associated with illusions, and that I should make the Moonlight Guild a group of illusionist assassins capable of summoning illusory duplicates or turning themselves invisible (With particles showing where they are, like with the Illusioner). They can also have bows/crossbows (Can't decide) so they have range.