Diamonds are the most valuable gems you can come across in Breath of the Wild. As well as fetching a high price from merchants, they are also used for dyeing and upgrading armour. But perhaps their most important use is in having the champion weapons remade when they break. This post describes the most reliable place in the game to find diamonds.
Ancient parts, especially ancient cores and giant ancient cores, are used in Breath of the Wild for crafting ancient weapons and arrows, and for upgrading the game’s powerful ancient armour. This post describes some easy locations that consistently provide the best drops of ancient parts, including drops of multiple cores.
Giant ancient cores are one of the hardest items to obtain in Breath of the Wild, but also pretty essential for acquiring and upgrading important weapons and armour. This post explains one reasonably fool-proof and safe way to farm them. The drop rate of giant ancient cores in this location over time is 1 in 8.