The Lemurian Vampire 3rd Case Achievement in The Case of the Golden Idol

You technically only need to find the clues required for the solution. Every clue in the game is marked with a ?/! and will turn into a check mark when you fully interact with them to find all the relevant details.

Solution:
Lavu Mata wanted to preserve the ancient practice and so accessed the sentinel's lodge using a basket and killed Tissa Gamini who had been sedated with honey. Afterwards, the murderer hid in a basket. In the next morning, the villagers found the skeleton of the dead ancient sentinel and became really afraid of Tower Dweller.