Randall:

“Right, Let’s hit it with my spiritual weapon and your shatter at the same time,” agrees Randall.  Coordinating his spell, Randall casts Spiritual Weapon and has it strike the phylactery!

Spiritual Weapon:  Attack: 19 Damage: 16

And a maximized 4th lvl shatter by Pepin for 40 thunder damage. DC20 con save:

A creature made of inorganic material such as stone, crystal, or metal has disadvantage on this saving throw.

A nonmagical object that isn't being worn or carried also takes the damage if it's in the spell's area.

And I'm going to roll it's object save at disadvantage for being made out of one of the materials mentioned in your spell.

It actually only has an AC of 19 and doesn't mention what it's save would be. But at disadvantage it will probably fail:

CON: 10 

So in a blinding flash of light as both the effects bombard the tiny statue it splinters into several pieces. One of which is the head which has two glowing onyx gems for the eyes.

The eyes continue to glow.

Randall:

Randall redirects his spell to try and crush the head and stop the glow in the eyes.

Spiritual Weapon:  Attack: 18 Damage: 14

Tempe lets his radiant sunbolts fly at the gems

Radiant Sun Bolt

To Hit 17

Randall's attack knocks the head about a little and Tempe's 1st attack only chips a loose piece off of the neck. However, Tempe's 2nd strike lands true and shatters the glowing eyes, it appears there was no further magical protection.

 "So how do we know if it worked and is truly destroyed?"

Tempe shrugs, with the wisdom of the ages answers with his own question "Perhaps, it, doesn't come back?"

Randall:

Carefully scanning for magical auras, Randall determines there are none.  “The physical form of the phylactery is broken, and the magic has faded from it.  I know of no other way to ensure the lich does not return, though I suppose we could consecrate the area.”

From all the research you're done so far you know that destroying the physical form of the lich is temporary but destroying the phylactery will permanently destroy the lich.

Perhaps because the site was hidden and guarded, or due to lack of time, whatever the real reason this phylactery wasn't as protected as you would have expected.

Randall:

”Shall we get to collecting books, then?  I can set up the Carpet of Flying as a book transport and we can walk next to it on the way back to the city,” offers Randall.

"We should look at what the puzzle was, maybe some artifacts can be garnered."

"Let's make sure all rooms are clear and save aswell before we leave." Pepin says willing to check out the corridors they haven't been to yet.

(So, what's our next task? The Goblin Horde has been sent home. Dracolich is dead, Phylactery destroyed. Original villagers from the beginning are resettled on an island to live happily. So seems like the danger is all averted. What's left for us to do?)

((I believe we were assuming a different entity was ahead of this all right? Creating the dracolich and such? We also had information about and old elven temple: https://www.dndbeyond.com/forums/d-d-beyond-general/play-by-post/102618-goblin-horde?page=202#c4031))

Yes, your immediate concerns were for the finding and destruction of the phylactery and then explore the old elven temple afterward.

And you guys all get the feeling that someone or something orchestrated the goblin horde, along with the dracolich... so... maybe a few more things to figure out before the happy ending.   :)

Quote from Brian_Avery >>

Yes, your immediate concerns were for the finding and destruction of the phylactery and then explore the old elven temple afterward.

And you guys all get the feeling that someone or something orchestrated the goblin horde, along with the dracolich... so... maybe a few more things to figure out before the happy ending.   :)

 (Excellent. Very happy for the campaign to go on. Let's maybe report back to the city and then head off to the temple?)

You are able to do a thorough search of the small complex and find that it is just the main chamber with the four hallways and other than what was previously described there is nothing here of any interest other than the many books littering the floor, with the few stacks that you guys made.

Gathering a bunch of books to transport back to Laurentiis will take a total of 2 days, and as previously mentioned you can always give directions to have the rest of the library salvaged.

Is there anything else you want to do before returning to the city?

What is the first thing you do upon returning to the city?