Although the main story of Horizon Zero Dawn is gripping from start to finish, it's hard to ignore the plethora of side-quests available to Aloy once she begins her adventure. From the moment she comes of age and prepares to take part in The Proving, NPCs around the world will have something for her to do to pass the time.
Some of these side quests are fairly simple, making Aloy use her Focus to find a missing person or tracking down certain materials that an NPC just can't seem to find, but there are others that are true tests of your skills in gameplay and may cause Aloy to perish long before her journey is complete.
7 Death From The Skies
This quest starts out like many other hunting quests, forcing Aloy to rid a region of Glinthawks that have been terrorizing the people. Like most other Glinthawk encounters, the machines will tend to gang up on Aloy and swoop down at her at the worst possible times, though, thankfully, the quest doesn't take place atop a mountain where she can be thrown off.
The quest doesn't end here, however, as once all of the Glinthawks have been taken care of, a Stormbird will appear to make Aloy prove she has the skills to brave the wilds of her homeland. Flying enemies can be relatively easy to deal with by using Shock, Freeze, or Fire arrows to shoot them out of the sky, but when it comes to the Glinthawk flock, you may need a different approach. The Ropecaster can be a godsend here, as tying down Glinthawks to keep them from swooping Aloy for a few moments will allow you to take care of the others without worrying about being hit from behind.
6 Redmaw
The battle with Redmaw had been teased for a while in the Hunting Lodge quests before you are actually given the quest, and for good reason. This Thunderjaw, while not as imposing as Corrupted variants of the machine, is still one of the more deadly encounters you are likely to face in the game simply due to the fact that it is a Thunderjaw.
Thunderjaws may be imposing, but they aren't impossible to defeat so long as you have some practice or know-how. Their sides are their weak spots, but the best way to approach these spots is by tearing off their weapons and tail to allow you to hit them uninterrupted. Using Freeze Bombs to make them weaker to damage for a few seconds also helps a lot, and the fact that you can't sneak up on Redmaw means that this is a good opportunity to use the Bomb Sling for massive damage.
5 Waterlogged
Most of the side quests in The Frozen Wilds DLC are fairly standard, with a few tough battles against newer enemies that come with a bit of a learning curve, but nothing is any harder than in the main game. The Waterlogged side quest, however, is a little different and can be the cause of a lot of frustration. Aloy is tasked with lowering the water level of Laulai's secret drumming spot, which is easier said than done.
This quest essentially boils down to a long-winded platforming section, which, despite what her training montage would suggest, isn't Aloy's strongest asset. With precarious drops into the water below, it is very easy to fall to your death and have to sit through Horizon's long load times on multiple occasions. The best approach to this side quest is to take it slow, as any attempt to rush through the dam area will likely result in failure more often than not.
4 Cause For Concern
Cause For Concern is easily one of the longer side quests to complete in the game, as it requires you to have cleared all bandit camps in the game - that aren't in the Cut - before confronting Nil atop a mountain. The bandit camps can be hard to deal with at low levels, but by equipping stealth enhancing gear and taking your time to pick off enemies one by one, you should have no issues with these at all.
After riding Aloy's home of bandits, Nil will challenge her to mortal combat, which you can either accept or reject. Taking up his offer will force you into a relatively easy, though sometimes irritating, boss fight against Nil where you will have to kill him for the fight to end.
Although there is a trophy attached to the final battle sequence, All Allies Joined, for having all possible allies in the final battle, Nil is, thankfully, not one of these allies, so killing him won't result in this trophy being unable to be unlocked.
3 Weapons Of The Lodge
This side quest begins as soon as you have access to the Hunting Trials and can be one of the more difficult side quests to complete, as you need to obtain a Sun ranking in all trials to get every reward. These rewards are golden variants of decent weapons, but there is a distinct lack of Sharphot Bow or Hunting Bow for stealthy kills. Instead, the weapons are focused more on trapping and control rather than damage output, with the exception of the Bomb Sling.
Surprisingly, each of these weapons is very useful in the Hunting Trials themselves, particularly the War Bow's elemental arrows and the Ropecaster's ability to tie down stronger enemies. It will take some practice and many trials may need to be repeated before gaining the highest ranking, but so long as you are using all you have learned in the game so far, you shouldn't struggle too much.
2 Queen's Gambit
Queen's Gambit is a very hard side quest to miss, since the quest that activates it, Traitor's Bounty, is given to you automatically during the story. After completing Traitor's Bounty, Aloy will be tasked with killing a machine that has been terrorizing the people, though this is easier said than done. The quest begins by taking on multiple Rockbreakers, which are a pain to fight one on one, let alone against multiple at once. The best approach is to find some higher ground where they can't erupt from the earth beneath you and pick them off from a safe distance, though this is only the beginning of your worries.
After defeating the Rockbreakers, you will be tasked with defending a large area from incoming enemies, ranging from humans to Corrupted Watchers, culminating in an epic battle with a Thunderjaw that just happened to wander into the battlefield. Like with the battle against Redmaw, the best approach is to tear off all of its weapons and use them against it by firing into its sides for the most damage, using Frost bombs or arrows to improve the damage output where possible.
1 Ancient Armory
Cause For Concern is a long quest due to how spread out the bandit camps are and how many of them there are, but Ancient Armory is long for a completely different reason. While the promise of a unique, high tech armor set would make most people want to power through the side quest and obtain the Shield-Weaver armor as quickly as possible, many of the Power Cells needed to open the door are locked behind story quests.
The first two Power Cells can be found relatively early, with one inside All-Mother that can be obtained after being attacked by Helis, while another can be seen in the opening sequence when Aloy is a child, though has to be returned to once she is an adult to actually reach it.
The final three Power Cells are all locked behind main quests: Maker's End, The Grave Hoard, and The Mountain That Fell, meaning that you can't actually obtain the Shield-Weaver armor until right before the final battle. Thankfully, if you missed the Power Cells the first time around, these locations can all be returned to, to ensure you can complete Ancient Armory without having to start a new game.