Z'Ant says they've set a trap for the Rapax assassin, and I know the room he's talking about but can't find where to actually "use" the rapax perfume. He said something about a rapax figure they used before, but I can't find that anywhere and Z'Ant won't respond to me asking about it. How am I supposed to do this mission? I understand the concept but can't understand it in terms of game mechanics.

Look in the rooms next to the trap... you should find some clues there...
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there is one lever with a picture of a Rapax, pull it, that should make things clear...

Did you find the 'hidden' entrance to martens bluff? You can't find the figure if you only entered the main entrance.
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There's a catapult outside martens bluff. Use it to get inside.