There are a lot of hidden achievements you can get in the House of Ashes. One of them is the Old Dog Trophy guide. It is one of the ultra-rare achievements, and you can only get this achievement if Balathu makes two kills using his spear.
In the Prologue, there is a slave that will be kicked out of the platform. As the slave is running away, the game will teach you how to aim and throw your spear. You have to kill the slave using the spear and make sure that it cannot run away.
In the Strange Aeons chapter, you will be given a choice of whether to advance or retreat with Nick. Choose the retreat option with nick as you are planting the charges. After this sequence, you have to choose whether to go after Salim or not.
Choose the Forceful option in this set of dialogue to go after Salim. After you save Salim, you will be confronted with Balathu. He will throw his spear to you. Do not press any button and you will get killed by Balathu’s spear. Afterward, you will get the Old Dog Achievement.
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