At lvl 70, you can (and should) start the Undermountain Campaign. Go to Sergent Knox and read the note behind him. You will get free gear that is better than anything you got so far. In Undermountain, you will level up to 80. When you finish the campaign, you will have access to expeditions, in which you can find some the best items in the game ! Do not start the Avernus campaign until you have proper companion gear from these expeditions (and good bonding runestones).
The following items are very good and you should try to get them ! Companion gear is especially important. You get tons of stat points through companion gear (via an augment companion and bonding runestones). This is the place where you get proper companion gear, nowhere else (it’s a shame : newer players would really benefit from having good companion gear in dungeons…).
- Arcturia’s Music Box : 1500 Power, 1500 Armor Penetration, 3000 Combat Advantage. Active : summons 2 mimics that deal damage and eat minions.
- Jhesiyra’s Tattered Mantle : 1960 Accuracy, 1960 Combat Advantage, +5 CON
- Trobriand’s Conduction Cable : 1960 Critical Strike, 1960 Combat Advantage, +2 STR, +2 INT
Set bonus : when you use a daily power, you deal 15% more damage to enemies on which you have combat advantage on for 10s. Loot from Zok boxes.
- Staff of Flowers : 3000 Power, 1500 Critical Strike, 1500 Awareness. Active : creates a ring of flowers around you, friends in the ring will get 10k more Power and Critical Strike, enemies are damaged and slowed.
- Woven Vine : 1960 Critical Strike, 1960 Critical Avoidance, +5 CON
- Blooming Cord : 1960 Critical Strike, 1960 Awareness, +2 WIS, +2 CHA
Set Bonus : when you use a daily power, creates a rune on the ground for 6s, people standing on the rune will get 5k more Awareness and Combat Advantage and become immune to control effects. Loot from Zok boxes.
- Wyvern-Venom Coated Knives : 1500 Armor Penetration, 1500 Critical Strike, 3000 Accuracy. Active : deals damage to enemies around you and poisons them for 10s. Poisoned monsters deal 12% less damage and take 12% more damage.
- Wyvern Eye Necklace : 1960 Critical Strike, 1960 Awareness, +5 CON
- Wyvern-Skin Belt : 1960 Armor Penetration, 1960 Deflexion, +2 DEX, +2 INT
Set Bonus : when you use a daily power, creates a rune on the ground for 6s, people standing on the rune will get 5k more Power and Armor Penetration and will deal 5% more damage. Bought from the campaign store.
- Scavenger's robes (861 ilvl) : 1% Power (actually 1% of your Power without your pet summoned, so closer to 0.75% of your total Power) for 10s when you hit or heal your target for more than 10% of your maximum HP (stacks 10 times, getting a new stack does not renew the others and you get a maximum of 2 at a time with an aoe), 1722 Armor Penetration. Obtained by farming runic encounters in the Lava Fields (Undermountain), or opening Slime-Covered Gear Packs (from the Undermountain campaign store) with a lvl 75-77 character (more and you get ebonized).
- Stealer of the Star’s Hide (armor, 1000 item level) : 1000 Armor Penetration, 1000 Critical Strike, 800 Critical Avoidance, Butcher’s Might : when you damage or heal for more than 15% of your max health, you gain 1% of your base Power (Power without your companion summoned) for 10s, max 5 stacks (independant stacks). Loot from ME's and Zok Boxes.
- Ebony Stained Hide (armor, 882 item level) : 1764 Armor Penetration, Butcher’s Might : when you damage or heal for more than 10% of your max health, you gain 1% of your base Power (Power without your companion summoned) for 10s, max 10 stacks (independant stacks). Loot from Master Expeditions, or LoMM (epic dungeon).
- Ebonized Scalemail (armor, 882 item level) : 1764 Deflection, Butcher’s Might : when you damage or heal for more than 10% of your max health, you gain 1% of your base Power (Power without your companion summoned) for 10s, max 10 stacks (independant stacks). Loot from Master Expeditions, or LoMM (epic dungeon).
- Trapper of the Twilight’s Braces (1000 ilvl) : encounter powers do 3% more damage, 1k Armor Penetration, 1k Critical Strike, 800 Critical Avoidance. Found in Zok Boxes.
- Ebonized Raid Ring (ring, 882 item level) : 6350 Critical Strike, 4234 Combat Advantage, Sniper’s Perk : ranged powers deal 3% more damage (can stack twice). Loot from Master Expeditions.
- Ebonized Restoration Ring (ring, 882 item level) : 3175 Defense, 7409 Critical Strike, Sniper’s Perk : ranged powers deal 3% more damage (can stack twice). Loot from Master Expeditions.
- Ebony Stained War Shirt (clothes, 882 item level) : 1764 Critical Strike, 1764 Accuracy, Charged Fury : when your stamina is over 75%, you deal 3% more damage. Loot from Master Expeditions.
- Shirt of the Champion (clothes, 1010 item level) : 4040 Critical Strike, Encounter Reprieve : 10% chance on critical strike to reduce encounter cooldowns by 1s (once every 5s). Loot from Fragment Expeditions, or from Treasure Maps in Avernus Wastes.
- Pants of the Sentinel (pants, 1010 tem level) : 4040 Defense, Critical Charge : 10% chance on critical strike to gain 25 action points (once every 5s). Loot from Fragment Expeditions, or from Treasure Maps in Avernus Wastes.
The complete list can be found in the Undermountain’s Companion Gear collection in Undermountain. You can complete the stardock questline (The Teachings of Zerthimon) on multiple characters to get a single stat 1010 item level companion gear of your choice each time. Almost all of the companion gear items are bound to account (and do not bind to character), and can be transfered to any of your characters at will. Found in Warden Expeditions and in Zok boxes. Note that the companion gear can also loot from Zariel's Challenge (very end game Trial).
Once you have completed the full Undermountain campaign, after completing your very first Master Expedition, you should meet Runemaster Sinyé and do the Boundless Runic Corruption quest. This quest will give you the item necessary to collect resonances in Undermountain Runic Encounters, and let you open the chest at the end of any expedition, assuming a rune was used and you have the quest for that expedition.
There are 3 types of expeditions in Undermountain : Master Expeditions (ME’s, repeatable 3 times a day) in the Yawning Portal, and Warden Expeditions (WE’s, repeatable 2 every 2 days) and Fragment Expeditions (FE’s, repeatable 2 every 6 days) in the Stardock (unlocked with the quest A Light in the Sky, after you complete the Undermountain campaign). It is very recommanded to do expeditions with 1 rune, in order to get Zok boxes, to gain extra rewards (RAD, equiment, companion gear, artifacts…). Runes are made on the altars at the start of an expeditions, with 10 crystalized resonances of the same type. Crystallized Resonnances are obtained in runic encounters, throughout Undermountain.
How to get Crystalized Resonances ?
After you finished the Undermountain campaign and completed your first Master Expedition, you need to talk to Runemaster Sinyé (close to Obaya Uday, on the same floor, next corner). She will ask you to collect resonances in Runic Encounters (the big coloured bubbles you’ve seen around Undermountain) and a Runic Resonator. To get the resonances, simply go to any runic encounter and hit monsters (no need to kill them, just hit them, a lot). The Runic Resonator requires you to kill monsters though. Once you have completed that quest, you can take the next one… and forget about it (it’s not worth it). Taking the quest will let you collect more resonances in runic encounters. You need 10 resonances of the same type to be able to make one Crystalized Resonance (on the altars at the start of any expedition). It sounds like a lot of work, but getting plenty of resonances is actually pretty fast.
Master Expeditions (ME)
The quest is given by Obaya Uday, on the first floor of the Yawning Portal. It can be taken 3 times a day. In these, you have to collect 9 relics (3 in each zone, you cannot go back so make sure to collect them all) in order to get the best rewards from the quest. You often get pieces of gear as rewards from the mini-bosses. But the best rewards are the +% damage gear, and the Rune Etching from the chest at the end (used to get a box from Zok). Make sure you have completed the Boundless Runic Corruption quest from Runemaster Sinyé to be able to use Crystalized Resonance and collect the chest.
The Teachings of Zerthimon Quest
This quest, obtained in the Stardock, requires 12 days to complete. It will reward you with a choice of a companion gear with 12k points in a single stat, bound to account (never binds to character, so you can tranfer it from character to character whenever you want). You can do this quest on every of your characters to get many of them.
To complete it, you need to collect Illithid and Githyanki Intelligences (once a day). Every 2 days, you'll be able to do an Illithid and a Githyanki Warden Expedition. Every 6 days, you'll be able to do both Fragment Expeditions. Repeat this process to get 2 Illithid and 2 Githyanki Fragments, and you'll be able to collect your reward !
You can take the quests and complete them another day. There's a limited number of Reconnaissance Quests, so you cannot hoard 20 of them, but there is no limit to the Intelligences and Rod Sections you can carry, and as long as you have 2/3 of them, you can pick a new Warden/Fragment Expedition quest. So, you can do your Reconnaissance Quests every day, and all of your Warden and Fragment Expeditions on the last day if you feel like it. You can keep doing Reconnaissance Quests and Warden/Fragment Expeditions once this quest is over, but you will not gain new companions gear from extra Fragments.
Warden Expeditions (WE)
The quest is given by Yrlakka in the Stardock. In order to be able to take the quest for a Warden Expedition, you need 2 Illithid or Githyanki Intelligences (which you get in Reconnaissance Quests). So you can do them twice every two days, or do plenty of Reconnaissance Quests and do all your Warden Expeditions whenever you want (as long as you have Intelligences). You do not need to collect relics for these, but the end boss is a bit stronger. The end boss always loots a piece of companion gear (maximum quality being 1010 item level epic, listed under Undermountain’s Companion Gear in the collection). All of the pieces are bound to account (and do not bind to character, so you can send your main character’s companion gear to a completely new character if you want a fast progression with them), with the exception of 965 item level companion gear (which are the ones I recommand buying on a new leveling character).
Fragment Expeditions (FE)
The quest is given by Yrlakka in the Stardock. In order to be able to take the quest for a Fragment Expedition, you need 3 Illithid or Githyanki Stardock Rod Sections (which you get in Warden Expeditions). So you can do them twice every six days, or do plenty of Warden Expeditions and do all your Fragment Expeditions whenever you want (as long as you have Stradock Rod Sections). You do not need to collect relics there either, but the end boss is a lot stronger. The end boss always loots a piece of clothes (pants or shirt, maximum quality being 1010 item level epic, listed under Rings of Undermountain in the collection… don’t ask me why). Note that the pants and shirts can now also be obtained from Treasure Maps in Avernus Wastes.
Now, the biggest rewards come from Zok boxes. In order to get them, you need to complete any expedition with at least one rune (Crystalized Resonance) used at the start of the expedition. This will allow you to open a chest at the end of the expedition. You can enter any expedition, as long as someone in the group has the quest to start the expedition, but you can only open the chest if you have the quest for this expedition. In this chest, you will receive rewards corresponding to the type of runes used, plus a Rune Etching. This Rune Etching has to be brought to Zok, a little guy hiding below the stairs at the Yawning Portal. He will reward you with 5500 RAD, a potion, and an item. This item can be one of the best artifacts in the game (Staff of Flowers or Arcturia’s Music Box, or their associated belt or necklace), a piece of gear (highest item level being 1000, listed in the Antiquities of Undermountain in the collection), a piece of companion gear (same as in WE’s), or a vanity pet. Of course, it’s totally random. So, cross fingers to get the things you want ! With all the expeditions, you can get an average of 4.33 Zok boxes a day (that’s almost 24k RAD, not bad !). Always do your expeditions with one rune (more make things unnecessarily hard for no better rewards). Always group up for expeditions with runes (unless you are an experienced player with a good and well equipped companion, expeditions with 1 rune are hard to solo).