Though many of its competitors fall into the "power creep" trap - when newly released characters make older, weaker characters obsolete - Genshin Impact is one gacha RPG where every hero is endgame-viable. Genshin undoubtedly has its superstars but even the starter units can hold their own. Your effectiveness is only partially dependant on the characters on your team, an even larger factor determining your success is which artifacts those characters possess.
Artifact farming is a chore that'll take up most of your time as a late-game player, and since artifact domains drop randomized loot, the amount of time spent by one player or another varies. However, each domain has clear-cut strategies and "leyline disorders" (i.e. buffs and debuffs) you can take advantage of to make the process speedier. You'll also get better rewards more often if you're doing the most difficult domains after adventure rank 45.
Updated December 27, 2021, by Joseph Burrell: With the introduction of a new five-star character, especially one as popular as Itto, comes a new wave of Genshin players rushing to grab the best domain gear. The Slumbering Court is where you'll find optimal artifacts for Inazuma's baddest geo mobster, but will you actually use him to farm there, or have Kokomi mains had the last laugh? Here's what you need to know before artifact farming.
9 Midsummer Courtyard (Electro Artifacts)
Overload creates additional blasts that damage enemies, while superconduct triggers a lightning strike harmful to you alone. You'll start off surrounded by five large electro slimes, they're relatively non-threatening, as usual, but the aforementioned leyline disorder punishes cryo carelessness.
Diluc will shine here, so will Klee, Yanfei, and Yoimiya. However, ranged attackers should beware of the second wave of cicin mages and Genshin's imprecise auto-targeting. Defensive units aren't necessary, but if the incoming damage is too much then Noelle, Zhongli, or Ningguang are great for non-reactive shielding. Diona is also viable, since her shield can block the lightning strike superconduct triggers, though it's better not to depend on her elemental burst for healing here.
8 Valley Of Remembrance (Anemo And Healing)
Valley's physical damage bonus is a boon for Eula mains, as well as physical-build Keqinqs, Razors, Beidous, and Crescent Pike-wielding Rosarias. Valley is among the least complicated domains because it lacks a negative leyline disorder effect.
If you're comfortable panning the camera to keep the fatui agent in your periphery then you can focus on the cicin mage first, for the sake of eliminating its annoying cicins. The fatui agent is only dangerous if he sneaks up on you. Tracking him can be tricky depending on your platform of choice, so prioritize enemies as you see fit. The treasure hoarders can be used to refresh "on-kill" buffs if your weapons have any, or they can provide slow-moving projectiles for Beidou to counter easily.
7 Domain Of Guyun (Geo Artifacts)
Much like Midsummer Courtyard, Domain of Guyun rewards certain reactions and punishes others. This time superconduct causes extra damage against enemies, while melt and vaporize - the game's strongest elemental reactions - will harm you.
Nevertheless, this domain is a cakewalk for Fischl, Sara, Raiden, Ganyu, or even Ningguang - the lattermost can attack the ruin hunter without chasing it or needing to manually aim. The last two cryo mages will tempt you to use melt reactions, but stick with superconduct and their shields will break in no time.
6 Hidden Palace Of Zhou Formula (Pyro Artifacts)
Melt triggers an explosion against the enemy, whereas overload triggers an explosion against you. Fan-favourites Raiden and Fischl are probably best left benched here - thanks to the pyro slimes, pyro mages, and blazing mitachurls - or they'll be punished by overload each time their skills activate.
These two can be utilized if a strong shielder is available, such as Zhongli or Diona, but attackers such as Kaeya, Ayaka, or Rosaria trivialize this challenge without much need for defensive measures.
5 Clear Pool And Mountain Cavern (Physical And Burst)
Steadfast, unreactive, resolute as a mountain... geo mains reign supreme at the cavern. Venti is also an excellent choice for this domain, but that goes without saying since he cleans up most domains effortlessly. Swirl reactions are useful here since you're faced with three abyss mages, each one weak against another's element.
Geo characters also receive a generous 75 percent elemental damage buff from the leyline disorder with no negative trade-off. A Ningguang with any constellations will be able to deal highly potent area-of-effect geo damage. Stand near the outer wall so that the mages teleport close together then unleash your AoEs with Ningguang or Zhongli.
4 Peak Of Vindagnyr (Cryo And Hydro)
Standing on the heated tile is far less important than staying off of the chilled ones. Although the threat of sheer cold is ever-present, with enough damage (especially pyro damage) you can easily clear this dungeon before the frost chips away at your HP.
The usual suspects are up to bat: Diluc, Bennett, Xiangling... anyone who can contribute to, and take advantage of, pyro elemental resonance. If you're without a pyro main-DPS then swirl teams can substitute. The Peak is widely seen as the easiest top-level domain, further contributing to the DPS dominance of Ganyu and Ayaka, who are geared up easily here.
3 Ridge Watch (Defense And Physical)
This domain rewards defensive play, which isn't a common occurrence in Genshin Impact, so bring out your Xinyan, Ningguang, Zhongli, Diona, or Beidou and watch your enemies beat themselves up.
This leyline disorder damages enemies every time they attack your shield. No shields? (Quit sidelining Noelle... she only wants to help). No problem! This whole fight is nothing but two geovishaps, who'll drop crystallize shields when hit, pick them up to benefit from the leyline disorder, even if you aren't using shielding characters.
2 Momiji-Dyed Court (Energy Sets)
Pyro and cryo characters are explicitly buffed by this domain's leyline disorder (60 percent bonus damage for standing on the appropriately colored tile), but once again, anemo characters also perform admirably thanks to swirl.
Any pyro or cryo five-star unit will rip through this domain if you're standing on the corresponding tile, and especially if Bennett is providing his ATK buff. Alternative strategies are as simple as dropping a Xiangling pyronado and/or Guoba, then following up with a burst from Xiao, Kazuha, Venti, or Sucrose to deal swirl and overload damage to the electro lawlachurl and abyss mage.
1 Slumbering Court (Defense and Healing)
Mihoyo seems to take one of two approaches when designing domains: the enemies and leylines either directly punish the characters who want that domain's loot (e.g. Beidou and Fischl struggle at Midsummer Court), or the domain will be custom-made for one character to breeze through.
Kokomi may not be as popular as other five-star characters but anyone farming this domain will be glad to have her. The new Rifthound enemies here are swift and numerous. Their poison debuff is a good reason to have a healer. The leyline disorder rewards electro-charged reactions so bring an electro and hydro character too. Kokomi fulfills both of these requirements, as do Barbara and Xingqui to a lesser extent. When the large Rifthound and Mitachurl spawn, focus down the former, it's the more threatening foe and you'll regret losing sight of it if you're watching the Mitachurl instead.