How can my players get around the Jackalwere’s pesky shapeshifting?


Context

I am designing a town for my play group to eventually travel to after they learn 2 NPC allies of theirs disappear after promising to come back from the town in question and they discover the NPC’s wagon off on the side of the road, clearly attacked with all goods and the NPC’s taken. The trail goes cold and knowing they aren’t far from a town, they go to the town only to discover that it’s basically a refugee encampment of people hiding from a Lamia and her Jackalwere. I have devils basically running the town holding people hostage for their own amusement with a clever human merchant having struck a deal of tribute with the Lamia in order for people to survive so long as they sacrifice so many people in a month.

Actual question

So here’s my problem, Jackalweres (MM, p. 93) have the Shapechanger ability that allows them to shapeshift into 3 forms: their true jackal form, a specific human’s form, or a hybrid form. This shapeshifting is what allowed them to infiltrate and destroy the other local villages in my campaign, however I need some way for my PCs to defend Honava (the last village in the area) from infiltration in some practical and believable way.

How can my players combat the creature’s shapeshifting?

Restrictions

My party will only have access to Lvl 3 spell slots. I have a Bard of the college of whispers, a Fighter who is a Monster Hunter, a Warlock who made a pact with a Great Old One, and a warlock who made a pact to become a Hexblade Warlock.

None of my players have access to truesight. Due to how I have the area set up for the level my players will be at (Level 5 or 6), no devil (CR 5 and lower) in the area has truesight, and true seeing is a 6th-level spell that my players aren’t at a high enough level to have access to.

My main question is this:
What other methods are there for dealing with shapeshifting/polymorph effects at lower levels?

Shapeshifting and custom moves as a Druid in Dungeon World – am I doing it right?

I’m playing Dungeon World for the first time, and chose a Druid. If I’m understanding correctly, for a Druid who has shapeshifted into another form, available moves fall into two categories: (1) normal moves still available to my character (basic moves, class moves, etc), or (2) custom moves available to this animal form.

1) Normal moves still available: While shifted, basic moves still cover a lot of, well, the basics: Hack and Slash, Defy Danger, etc. If I turn into a bear and take a big swipe with my razor-sharp claws, there’s no reason to develop a ‘custom’ move for that – Hack and Slash still serves just fine.

2) Custom moves: However, if (still in bear form) I need to climb a tree to escape a danger on the ground, I’m now using a custom move that the bear shape provides me: Natural Born Climber. In my natural form, that might be a Defy Danger roll to try and make it up the tree … but bears don’t have to TRY and make it up a tree, they just DO it. So, in bear shape I spend a hold, and I just climb the tree (no roll needed).

The actual custom move would look like: Natural Born Climber – with your powerful haunches and razor-sharp claws, you easily climb almost anything that will ‘bear’ your weight.

I understand each animal’s custom moves are subject to GM’s approval. I’m just trying to ease his burden by developing a bunch of ‘stock’ custom moves for certain animals that I expect to rely on frequently (Fly, Swim, etc).

To reiterate: am I handling the different types of moves right? If not, what should be different?

Thanks in advance