I wrote more comments about my Breath of the Wild Uber Challenge video than I can fit in a YouTube description, so I put the level-by-level comments on this page. See the YouTube description for general comments.
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Lightning Levels
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The lightning levels are pretty easy and boring, so you may want to skip ahead to the fire levels, which start at 8:20.
Level 1: Within the trial, each box with arrows contains two bundles. Each bundle can contain either 1, 5, or 10 arrows. The four arrow bundles in this level each gave me a single arrow, which is the worst possible luck. If you're really unlucky with arrow drops throughout the trial, you might run out of arrows. However, I got some good drops later in the trial, so the bad drops here were tolerable.
Level 2: I make sure to pick up the Royal Guard's Sword, which will be useful in the Igneo Talus battle.
Level 3: Unlike the boxes, each barrel with arrows always contains the same number of arrows (5). The Moblin Arms are useful for breaking containers, but they take up space in my inventory, so I only grab two.
Level 4: The game handles many enemies using the "out of sight, out of mind" rule: as long as the enemies aren't on screen, they won't attack you. So, I point the camera away from enemies to prevent them from bothering me. I use this trick in a few levels.
Level 5: You can conserve the durability of the better weapons by using bone weapons here, but I don't need the extra durability, so I use stronger weapons to beat the Stalnox faster.
Rest Stage: I use up two durability points on the Royal Guard's Sword to make the Igneo Talus battle easier (see the comments for that level for more details). I pick up some wood so that I can light fires in the snow levels.
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Fire Levels
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The fire levels took the most work to figure out. After 6.5 seconds, Link will catch on fire and take 0.5 damage. He will take another 0.5 damage every second until the fire is put out (but the clock runs slower while you're in bullet time). If you just play normally, the fire will kill you long before you finish all five levels. Fortunately, I discovered a few tricks to avoid damage:
* Falling in the lava puts out the fire and resets the 6.5-second timer. Normally, falling in the lava deals 1 damage. However, if you take 0.5 damage from the fire, then fall in the lava shortly afterward, the lava will not damage you. For this reason, before falling in, I wait until I take damage from the fire.
* Starting a spin attack with a heavy weapon (such as the Great Frostblade or Moblin Arm) puts out the fire.
* In addition, there are a few more obvious ways to avoid damage: the fire will be put out and the timer will be reset when a portal appears and when you enter a portal.
By using these techniques, you can preserve most of your health.
Level 1: I use all of the aforementioned techniques to get through the level with only 2 hearts lost. 1.5 might be possible if you shoot the Octorok without entering bullet time, but bullet time makes it much easier to kill him.
Level 2: Probably the easiest of the fire levels. I simply fall in the lava after killing each Lizalfos to put out the fire.
Level 3: The Great Frostblade's ability to kill fire enemies in one hit comes in handy here. After taking out the Wizzrobe and the Moblin, I attempted to use a spin attack to put out the fire. However, I started the spin too early, so Link wasn't on fire yet (but he caught fire shortly afterward). After I noticed that I was taking damage, I stopped the spin attack and started another one. The mistake cost me 1.5 hearts.
Level 4: This level is the hardest fire level (and probably the hardest level in the challenge), mainly because the Moblins' behavior can be tough to predict. I need to take the Steel Lizal Bow from the first Moblin so I can quickly kill some enemies later in the trial, but if he's standing right next to the edge of the platform, he sometimes drops it into the lava. Luckily, he stood far from the edge, so I was able to get the bow after killing him. Taking the other Moblins' weapons (the Royal Guard's Spear and Knight's Claymore) is less important, but it makes thing easier in later levels, so I was glad to get both of those weapons here. I utilize a useful technique in this level and a few others: if you unequip and reequip an elemental weapon like the Great Frostblade, the weapon's elemental power will be immediately restored. The last Moblin took some extra time to kill because he fell down to the middle level of the tower, but the level went pretty well overall.
Level 5: There are a few things to watch out for in the Igneo Talus battle. If you spend too long on top of the Talus, he will throw you off, wasting a lot of time (and hence hearts). Also, while you're on the ground, it can be tough to approach the Talus since he can throw his fists at you or pound the ground next to you. To kill him quickly, I use the Royal Guard's Sword. Before reaching this level, I used up two of the sword's durability points. If the sword is pristine when you start attacking the Talus, he will often throw you off before the sword breaks. But since I've already taken off a few durability points, it breaks sooner, allowing me to avoid being thrown off. When the sword breaks, it deals a critical hit, which stuns the Talus for a few seconds. During this window, I jump off the Talus, enter bullet time, and finish him off with the Steel Lizal Bow.
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Snow Levels
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In these levels, Link takes 0.5 damage every 10 seconds (but the clock runs slower while you're in bullet time). Unlike the fire damage timer, the cold damage timer does not reset when a portal appears or when you enter a portal. The only way to reset it is to warm up by going next to a fire. You can keep a fire burning by igniting a bundle of wood (to create a campfire) or igniting a wooden weapon. Campfires will never burn out, but they can be easily destroyed by enemies. On the other hand, wooden weapons can't be destroyed by enemies, but they will burn out after one minute. You can reset the one-minute timer by putting out the fire.
Level 1: The Steel Lizal Bow allows me to kill the Blue Bokoblins in one hit. The Stone Smasher lets me kill the Pebblits in one hit.
Level 2: At the beginning of the level, I throw a couple wooden spears near one of the explosive barrels. Then, I throw the barrel down to blow it up and ignite the spears. The explosion can send them far away, so I like to use two spears instead of one to have a better chance that at least one of them won't be sent too far. Once the spears are burning, I use the fire to start a few campfires, which burn forever as long as they aren't disturbed. Then, I fight the Silver Moblin. He has a lot of health, but you can kill him faster by lighting your weapons on fire. I make sure to keep two wooden spears for later use. Note that the cold damage timer doesn't reset when you enter the portal, so I carry a fire all the way to the portal to give myself as much time as possible in the next level.
Level 3: Although I don't have fire arrows, I can still light a regular arrow on fire and use it to kill the Wizzrobe in one hit. When fighting the Silver Bokoblin, I prefer to use spears because each hit stuns him, making it easy to keep him at bay. Once he's dead, I make sure to grab all the weapons (especially the Blizzard Rod) so that the Moblin can't use them against me.
Level 4: No tricks here; I just keep shooting the Frost Talus until he dies. Once again, the Steel Lizal Bow comes in handy; with a weaker bow, it would take more time, more hearts, and a lot more arrows to kill the Talus.
Level 5: Many of the Lynel's attacks can kill you in one hit, so you have to be careful. Until the Lynel uses his fire attack, my strategy is simply to use my strongest weapons to deal damage as fast as possible. Once he starts the fire attack, I drop a few wooden weapons on the ground so that he'll ignite them. From then on, I can avoid cold damage by either staying near the burning weapons on the ground or lighting another weapon and holding on to it. However, the weapons will burn up in one minute, so I must keep that time limit in mind. After killing the Lynel, I start a new fire and put out the old ones to reset the timer and prevent the weapons from burning up.
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Grass Levels
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With the exception of the last level, the grass levels are pretty easy. However, you have to be mindful of your supply of weapons and arrows. If you're running low on one (especially arrows), try to conserve your supply by using the other where possible.
Level 1: The Decayed Guardians pose little threat, but use up a lot of weapon durability. The Knight's Claymore and Iron Sledgehammer, weapons which I sometimes don't manage to pick up, are nice to have, but not necessary.
Level 2: I like to stun the Guardian Stalker with a critical hit while approaching it in order to make it easier to chop off its legs. This time, I didn't have a whole lot of arrows, so I mostly used melee weapons once the legs were gone.
Level 3: Easy.
Level 4: I take out the turret first so it doesn't bother me while I'm fighting the other enemies. While I was fighting the Skywatcher, it briefly lost sight of me, so it fired its laser much faster than usual. Luckily, a treasure chest took the brunt of the blast and I only took one heart from the explosion.
Level 5: There are quite a few dangers in this level. The Lynel and the turret can both kill you in one hit. While you're occupied with them, one of the many mounted Bokoblins can get behind you and attack you, which will usually be fatal. If you stay away from the Lynel, he might pull out his bow, which is by far his deadliest weapon. I came up with a pretty good strategy, though. At the start of the level, I sprint toward the Lynel, causing him to pull out his spear instead of his bow. He'll use his fire bomb attack right away; if I'm lucky, the attack will kill a bunch of Bokoblins. Around the same time, the turret will fire a laser. Using the burning grass from those attacks, I float up with the Paraglider, stun the Lynel with a headshot, and take out some Bokoblins with arrows. Once I'm on the ground, I focus on killing the remaining Bokoblins while getting out of the turret's range. With the Bokoblins dead and the turret too far away to hit me, I can concentrate on killing the Lynel. Once he's taken care of, the turret is easy prey (although I had trouble landing headshots for some reason).