During the Main Quest, "The Broken Sky" in Horizon Forbidden West, Aloy must slay a group of Rebels and their tamed Tremortusk, a massive machine resembling a mammoth with four tusks. This mechanical beast moves slowly but is equipped with heavy armor plates and multiple ranged weaponry, making it a formidable force to be reckoned with. Extremely dangerous in close combat, the Tremortusk in Horizon Forbidden West will stomp and smash anything or anybody in its path. Therefore, a reasonable strategy would be to attack it from a distance while exploiting its weaknesses.
As mentioned above, several Rebels are in the area, causing them to be a threat to the mission. While it's possible to ignore them and focus on fighting the Tremortusk boss, the seemingly slight annoyance they present can become a danger if they cause Aloy to stagger when the metallic beast is about to strike. As a result, it is recommended that players take out one or two before or during the first few minutes of the fight. Using the tall red grass in the vicinity for stealth kills would also be a good idea.
Once the boss battle with the machine in Horizon Forbidden West commences, the player should immediately seek cover from enemy ranged projectiles. Be sure to also keep an adequate distance from the Tremortusk's rampaging attacks, as it is able to bash down broken walls and other forms of cover.
The most crucial detail to note about Tremortusk is that it is vulnerable to Freeze. Thus, players should prioritize firing Freeze Arrows or using their Frost Blastsling to raise the Elemental weakness and freeze the monster. Alternatively, players can use the Chillwater Drum to glaciate the Tremortusk. Once it is frozen, any damage dealt to the boss will be increased.
Although Tremortusk is weak to Fire, players can set the hostile beast ablaze, including any nearby Rebels, by destroying its Blaze Sac located on the underside of its massive frame. Precision Arrows in Horizon Forbidden West would be an excellent choice for this feat, and having the Concentration skill will provide Aloy with extra time for more accurately aimed shots.
Finally, players can use their Sharpshot Bow's Tear Precision Arrows to shoot off the Tremortusk's weapon components and render its ranged systems useless. Be sure always to be moving and dodging, as standing in place while aiming is bound to place players on the machine's trampling path.
Horizon Forbidden West is available on the PlayStation 4 and PlayStation 5.