Artifacts are very expensive to upgrade. They require a total of about 500k Refinement Points (RP) each to reach Mythic quality. So, yes, you will need 2 million RP to upgrade all 4 artifacts. These are not a priority. Focus on your main hand weapon first and foremost. Then on your bonding runestones. Artifacts come later. Start with your active artifact, so that you can use a cool power to help you, then on your passive artifacts to get better stats. A green lvl 1 artifact is good enough for set bonuses.
They give you stats, but the main thing is their power. At Mythic quality, their cooldow is 60s. Do not forget to use them. Some of them are pretty powerful !
Active Debuff Artifacts
The most important of them are debuff artifacts. It’s important for endgame content that people use different debuff artifacts, because they do not stack if they are the same (unless they are at different quality !), but they stack together if they are different.
- Charm of the Serpent : attacks enemies in a cone in front of you, reduces targets’ damage resistance by 16%. Loot from T9G.
- Halaster’s Blast Scepter : single target, stun + damage, reduces target’s damage resistance by 15%. Loot from ToMM.
- Wyvern-Venom Coated Knives : deals damage around you, poison for 10s, poisoned enemies takes 12% more damage and deal 12% less damage. Can be bought in the Undermountain Campaign store (in the campaign menu).
- Lantern of Revelation : deals damage around you, increases the damage they take by 10% for 10s. Quest reward (lvl 21 at Protector’s Enclave) or random loot in dungeons.
- Heart of the Black Dragon : deals damage to up to 7 enemies in a line in front of you and inflicts a damage over time for 6 seconds. Enemies take 6% additional damage for the duration.
- Token of Chromatic Storm : summons 9 chromatic meteors that will strike near your target’s location after a brief delay. Each meteor deals damage to nearby enemies and has a special effect depending on its damage type. One of them increases damage taken by the target by 10% for 10s.
- Vanguard's Banner : gives 2500 Power and Critical avoidance to allies, and reduces the monsters' damage resistance by 5%, for 30s in an area. Can be bought for 40k Glory (PVP currency), from Erik Sundershield, at the Trade of Blades in Protector's Enclave
- Thirst : lunge forward, deals damage to enemies, reduces targets’ damage resistance by 10% for 10s. Loot from Castle Ravenloft (difficult to handle because of the movement, which can be cancelled to avoid being in front of the monster, not recommanded if you can use another one).
Other Active Artifacts
- Sigil of the Paladin : creates a small AoE at your feet which increases damage resitance for the whole party by 15% and heals over time for 10s.
- Sigil of the Cleric : fills 25% of your next Daily power in 15s, and heals yourself a bit when you use encounter powers. Quest Reward (Vault of the Nine) at lvl 70.
- Defender’s Banner : allies gain 5k Power and Awareness, foes deal 5% less damage, for 30s. 40k Glory, from Erik Sundershield, at the Trade of Blades (Protector’s Enclave).
- Staff of Flowers : allies gain 5k Power and Critical Strike (it’s written 10k in the collection, but it’s 5k), foes are slowed and take damage every second for 15s. Loot from Zok Boxes.
- Aurora’s Whole Realms Catalogue : summons a vendor. Keep one in your inventory if you are not VIP 7. Quest reward (lvl 21 at Protector’s Enclave) or random loot in dungeons.
- Storyteller’s Journals : look below for more infos.
All of these can be used as a main artifact. The Sigil of the Cleric is very easy to get and a good artifact to start with : having your daily more often can be very convenient. The Sigil of the Paladin is the most useful to mitigate damage. The Aurora’s Whole Realms Catalogue is a good little trick for those who are not VIP rank 7 (only use it when soloing, you can’t change it that easily because of the cooldown).
Take into account the fact that active artefacts powers are limited to their rare (blue) version in scaled content (random queues). Only the cooldown and stats can be improved at higher qualities.
For passive Artifacts, you mostly care about the stats. The ones given to you at the start of Undermoutain at lvl 70 are good enough to start with. But eventually, you will take the artifacts from Undermountain (which are item level 300, while the others are only item lvl 150).
- Sword of Zariel : 3k Power, 6k HP, 1.5k Critical Strike. Loot from Zariel’s Challenge.
- Book of Vile Darkness : 3k Power, 1.5k Armor Penetration, 1.5k Deflection. Loot from TIC (The Infernal Citadel, mod 18 dungeon).
- Halaster’s Blast Scepter : 3k Power, 6k HP, 1.5k Critical Strike. Loot from ToMM.
- Trobriand’s Ring : 3k Power, 1.5k Defense, 1.5k Critical Avoidance. Loot from LoMM.
- Arcturia’s Music Box : 1.5k Power, 1.5k Armor Penetration, 3k Combat Advantage. Loot from Zok Boxes.
- Staff of Flowers : 3k Power, 1.5k Critical Strike, 1.5k Awareness. Loot from Zok Boxes.
- Erratic Drift Globe : 3k Defense, 6k HP, 1.5k Deflection. Bought from the Undermountain Campaign Store (in the Campaign menu).
- Wyvern-Venom Coated Knives : 1.5k Armor Penetration, 1.5k Critical Strike, 3k Accuracy. Bought from the Undermountain Campaign Store (in the Campaign menu).
The ones with Power are certainly the best, but the others are good if you need the stats.
That may also be the place where you will put an artifact to complete a set with your neck and waist items. These include :
- Sword of Zariel : gain up to 6500 Power as you lose HP, doubled when an ally dies. Only good for a healer… But really not fantastic, as you should have full HP most of the time and the Power boost is not that impressive.
- Shard of Orcus’ Wand : up to 10% more damage depending on the difference of HP% between you and your target (about 4% on average).
- Book of Vile Darkness : increase damage dealt by 2.5%, +2.5% against demons (Avernus, IC, Demogorgon…).
- Halaster’s Blast Scepter : When you stand still for 3s, your damage and movement speed is increased by 5%.
- Arcturia’s Music Box : 15% more damage if you have combat advantage for 10 seconds after using a daily power.
- Tarokka Deck : when you hit a single target with an aoe, it takes 5% more damage for 5s.
- Charm of the Serpent : up to 5% more damage if you move for 15s, removed if you stand still for more than 5s.
- Apocalypse Dagger (only available during the Day of the Dungeon Master Event) : whenever you hit an enemy with a critical strike, the target takes 1% more damage for 5s, stack 5 times.
- Tiamat’s Orb of Majesty : 5% more outgoing and incoming healing.
These are very situational. Look at which waist and neck you want first. The Book of Vile Darkness is best in Avernus. The Orcus set is still very good in scaled content. Any other can be good depending on your playstyle.
If you participated in the Tales of Old Event, you may have collected the 4 Storyteller’s Journals. These are the best artifacts in the game. They give lots of stats (though less than Undermountain artifacts). But most importantly, they give 2 set bonuses which boost your HP a lot and improve your damage a bit. If you have a set bonus with your waist and neck, you can still use 3 Journals and benefit from all of the set bonuses. If you do not have a set bonus with your waist and neck, you can either use 3 journals as passive + a good active artifact or all 4 journals with one of them as active.
Active Journal (if you unlocked all of their powers)
- Frozen Storyteller’s Journal : deals ice damage in an area, stuns enemies for 3.4s, summons 3 ice dwarves for 20s, increases your defense by 5%, increases the party damage by 5%. Best for a Devout Cleric.
- Envenomed Storyteller’s Journal : deals damage in an aoe, add a stackable effect when you attack (after 15s, the target takes 5% weapon damage times the number of stacks), stun enemies for 3.4s, summon an orb that deals poison damage, increases your damage by 5%, generates 20 AP every second for 15s (30% of your next daily). Best for an Arbiter Cleric.
- Envenomed Storyteller’s Journal : 750 Power, 750 Defense, 750 Critical Strike, 750 Combat Advantage.
- Frozen Storyteller’s Journal : 750 Power, 3k HP, 750 Critical Avoidance, 750 Armor Penetration.
- Flayed Storyteller’s Journal : 750 Power, 3k HP, 750 Critical Avoidance, 750 Accuracy.
- Darkened Storyteller’s Journal : 750 Power, 750 Deflection, 750 Awareness, 1.9% Companion Influence (about 300 in all stats).
- 2 or more : 1k Power, 10k HP for EACH journal equipped (yes, 4k Power, 40k HP if you have all 4 equipped), +1 to all ability scores.
- 3 or more : Do an additionnal hit for weapon damage on a critical strike (around 4k damage). Powers have a chance to deal 10% of your weapon damage.
That’s a total of about 7.5k Power and 46k HP + many other stats and bonuses. With the Undermountain+Avernus artifacts, you get 7k more Power at the cost of 40k HP… Considering Power has relatively low returns for a healer (because more Power = less critical chance), If you have the Journals, use them. If you don’t, let’s hope they become available again in the future.
Unfortunately, the Tales of Old event is not planned to come back in the near future. That said, the difference with Undermountain+Avernus artefacts is not extremely big. It’s mostly a trade between Power and HP.
Halaster’s Blast Scepter and the Sword of Zariel are on par with the Tales artifacts (less HP, but more Power, and Critical Strike, which is perfect for a Devout Cleric, if you do not need the HP).