This is my guide to getting 100% of the achievements for The Excavation of Hob's Barrow. I'm just a fan and player so am working from limited information so please comment if you have any more info and I will edit the guide. Many thanks.

NOTE: I've been informed by comments that the achievement Into the Night, which I've listed as story-related and unmissable is apparently possible to miss but to date I've been unable to recreate the circumstances where one would miss it. Plus I see it listed as unmissable in guides by other authors. All the same, be aware and make sure to save frequently just in case.

SPOILERS FOLLOW

These are achievements based on dialogue options, interactions with specific non-quest items or that you might otherwise not get during an ordinary playthrough. In approximate order:

The Slap: When you are propositioned in the opening act, slap Arthur.




An Ode to Tondbert: Clicking on the paintings in the Plough will get you this one, specifically the one featured in the achievement image (right side of the room).




A Curious Collection: Click on all of the decorative plates in the Plough (don't forget the one in your room).






Rest: Sit on the bench looking out over the moors (and continue sitting until this pops). It is apparently also possible to get this on day two also.




Feathered Friend: Pick up one of the hens outside Shoulder's cottage.




The Scholar/The Fool: Get all of Father Roache's Shakespeare questions right (The Scholar)/wrong (The Fool). These are mutually exclusive so to get both you'll either need to save before setting off with him and then re-load after to play through the scenario a second time or alternatively get the one you didn't get the first time on a second playthrough.

The answers to his questions are 1) Richard II, 2) Othello and 3) Romeo & Juliet. Get either all or none of these for the relevant achievement. The Father asks you the first and last questions when you go to and from Leonard Shoulder's house but he asks the second question when he sees you examine the moon carving on Leonard's door. This question, it seems, is miss-able, so make sure to examine the moon carving while the Father is still there.

Scandalmonger: The moment you are given the option to divulge Father Roache's medical problems to Mrs de Plancey, do so.



Hob's Barrels: This pops after you've drunk a number of ales with Mr Long (two or more), so don't rush to invite Cyril as that solves the puzzle and ends your ability to invite Long for drinks.



A Moment of Reflection: Sit on the bench looking out over the moors once you've learned about Margaret.



Hellebore: After you've completed the quest where you rescue the milkman, go back to the scene of the crime and collect the flowers. Present them to Mother Mildred.



Dauntless: Once you've done the quest to fetch the flowers for Albert's grave and you're asked whether you are afraid of death, answer that you are not.



Romance on the Moors: At the end of the quest where you procure some tarts, when James asks you to join him on the moors for a picnic, do so.



Zoolinguist: Immediately after the confrontation with Arthur and James in the alley near the end, interact with the horse.



Herbert: This should pop when you interact with Herbert the cat when he is on your room on the morning of the third day.



Abandoned: Head back out of the barrow after entering and you'll notice that you have been left on your own. Don't wander further in before first leaving or you'll miss this one.

These pop automatically as you progress through the story and complete story-essential quests. These are un-missable in a full playthrough. You will get them in (approximately) the following order:

Arrival: Arrive at Bewlay at the start of the game.
Into The Night: Follow the mysterious figure.

ADVENTUS: Begin day one at Bewlay.
The Bloodletter: Help the ailing Father.
Lockpicker: Get into the Post Office warehouse.
Fossil Collector: Add to the Blacksmith's fossil collection.
Hob's Barrow: Touch the barrow.

EXPISCOR: Begin day two at Bewlay.
A Family Connection?: Gather some important information from Mother Mildred.
The Mystery Man Revealed: Finally meet Mr Shoulder.
Permission Granted: Obtain permission to explore the barrow.
The Abandoned Fiddle: Collect the fiddle.
The Swap: Perform the swap of flowers.
Eunice the Provider: Get some goat milk.
Cartographer: Visited all of the areas listed in the map. You get this when you finally head to the extreme 'East' where you always turned back before.
Elopers: Reunite the lovers.

INCANTAMENTUM: Begin day three at Bewlay.
The Seal is Broken: Enter the barrow.
Temple: Complete a puzzle and enter the temple.
The Goat Below: Get by the goat.
Ceasing of the Racket: Solve the music puzzle.
The Final Descent: Reach the end of the underground chamber.

VINDICTA: Begin the final chapter.
Abraxas Rex: Complete the game.