Thank you Niggles & Levrifon for your answers :) I will try later, I have no one for a ritual sacrifice !
You could always sacrifice Lara. ;-P
On a side-note, I only now noticed this in the description on the game-card:
[...]this Tomb Raider game feels more like a Dan Brown novel than an Indiana Jones movie.
Who in their right mind thought that this is a good selling point?