Gear Review
Symphony of Blades is a strong option to provide your group members with sustain for their primary resource whether it be Stamina or Magicka. The application of the Symphony of Blades on the previous pre-CP 2.0 iteration of the Infinity build came from setting down a Blood Altar so the Minor Lifesteal could proc it. However this was changed by the developers so that Minor Lifesteal couldn't proc procs ("procs shouldn't proc procs").
Replacing heavy armor set Yolnahkriin somewhat in part due to the post-Flames of Ambition Armor Changes will be the medium armor set Powerful Assault. In addition to granting even more Weapon and Spell Damage to your group members, Powerful Assault will be kept up easily as you will need to use a specific healing ability to ensure Symphony of Blade procs. Note that Armor was updated so Medium Armor is fine in terms of mitigation.
Replacing the previous light armor set Olorime is one of the Rockgrove Trial sets, Stone-Talker's Oath - arguably the best group sustain set in the entire game.
While we are sacrificing a few hundred more Weapon and Spell Damage, we have to take note that a base 1000 Weapon and Spell Damage were added to all player characters post-Flames of Ambition and that many damage specs tend to favor parse foods like Ghastly Eye Bowl or compromise with Clockwork Citrus Filet/Witchmother's Potent Brew to sustain their rotations although this puts them at higher risk of death due to their lower health.
With Stone-Talker's Oath, we will indirectly help the DPS in our groups by giving them more Max Health and Max Magicka/Stamina through their usage of bi-stat food where they can comfortably sit at a higher level of Health with more than enough sustain.
Alternatives to Stone-Talker's Oath or even Powerful Assault can include Olorime and Alkosh still (due to the Penetration needed on trash in specific instances).
As we are using a variety of skills including Balance or Blood Altar if need be, an Infused tri-stat reduction enchantment is quite nice. The two other jewelry pieces can be Infused, Triune, Arcane, Robust or Healthy depending on your desired stats.
The one hander enchantment on the frontbar can be either Shock or Poison, the Poison enchantment can proc the Combustion passive from your Ardent Flame skill tree giving you 500 Stamina back upon application.
The backbar weapon can be a 2x item set of your choice but since you will most likely be casting Elemental Drain in groups of 3 DPS as that is fortunately or unfortunately the composition of most 4 man groups, the Vateshran Destruction Staff will give you free damage in addition to also activating the Magicka portion of the Combustion passive from your Ardent Flame skill tree giving you 500 Magicka back upon application of the Burning status effect. Moreover the Shock and Frost damage instances can apply their own respective status effects of Concussion and Chilled which can be of aid for both yourself and the group.
Skills Review
There's quite a lot to unpack here but the basics are present: Unrelenting Grip is your Magicka-based pull and soft aggro of any mobs in Dungeons or Arenas. This can be swapped out for a different skill depending on the situation for a heal such as Green Dragon Blood or more damage debuffs such as Stone Giant if possible.
We're going to be going with Pierce Armor over Ransack due to the fact that Pierce Armor gives both Major and Minor Breach which are incredibly useful to increasing group DPS as Penetration is an important value in ESO.
Choking Talons or Heroic Slash will take the same skill slot depending on the situations. Igneous Shield is your main method of regaining Stamina back by casting Magicka due to how your Helping Hands passive works in the Earthen Heart skill tree of the Dragonknight class.
Echoing Vigor will be your main heal for a majority of the time for both yourself and the group. It will be the primary heal that procs Symphony of Blades while also acting as the Assault skill needed to proc Powerful Assault. Luckily it has a 10 second duration which perfectly matches the duration of Powerful Assault and lines up nicely with the Symphony of Blades' and Stone-Talker's Oath cooldowns.
Your frontbar Ultimate will be Aggressive Horn which increases your group's Critical Damage through Major Force. Should you not need Magma Shell on the backbar as an Ultimate, you could do Aggressive Horn on the backbar and Sword and Board Ultimate on the frontbar for more sustain.
Balance on the backbar will act as your main skill to use for not just Major Resolve which increases your Resistances but also to gain Magicka back so you can use the Magicka for Unrelenting Grip or Igneous Shield to get Stamina back if need be.
At the same time you're doing all of this, your Stone-Talker's Oath should be activating every 10 seconds giving you both Magicka and Stamina to use to keep up your Health which is then used to recycle back into your casting of Balance. This all again plays into the recycling theme of the Infinity build.
Blood Altar is great to have as an emergency heal from its Synergy for other members while providing Minor Lifesteal to your group. Take note that this skill also costs Health to cast which is - in addition to Balance - where that tri-stat reduction enchantment kicks in. Depending on the situation this could be swapped out for other skills if need be.
Elemental Drain may provide the same Major Breach as Pierce Armor but it also offers Minor Magickasteal which is quite the sustain buff not just for any Magicka DPS in your group but also yourself. It's also needed to activate the optional Vateshran Staff for this build.
Inner Rage will be your ranged hard taunt.
Blockade of Frost is not only your main method of applying Infused Crusher for more armor Penetration on a boss for your group but also gives shields that absorb projectiles. Upon the usage of those shields if there are projectiles hitting anyone in your group, you gain 1800 Magicka back per person from those Frost Wall shields.
Craft
Warfare
Fitness
Champion Points Review
To see what each Champion Point does, hover over or tap each one shown in the allocation chart.
There can be quite a lot of alternatives for your 4th Warfare or Fitness Slottable (Swift Renewal and Bastion, respectively). It all depends on what you may want to try or may need for specific Dungeon boss fights or Arena stages (veteran Dragonstar Arena, veteran Blackrose Prison).
Salve of Renewal, From the Brink or Hope Infusion could certainly be interesting options to try depending on how you modify this build. Slippery, Unchained and Strategic Reserve could be notable fourth alternatives for your Fitness Slottables.
Introduction (Update 32, Deadlands)
Note: You do NOT need Perfected Gear to use this build at all.
The Infinity tank build since its inception in the Harrowstorm patch focuses on Dragonknight tanking strictly four man content on normal, veteran and veteran hard mode levels (Dungeons and Arenas).
This build is NOT recommended to take to Veteran Trials.
Infinity has an emphasis on providing crowd control, group utility and increasing your group's DPS while offering a near endless amount of sustain for yourself and the group.
The theme of infinite sustain is quite reliant on the interactions between the item sets and the Dragonknight class toolkit of "recycling" Magicka into Stamina, Stamina into Magicka and providing more for your group beyond the usual taunt and block.
For a beginner's guide to tanking in The Elder Scrolls Online, you can refer to this guide.
Recommended Races for this build are Imperial, Nord, Argonian, Breton and Redguard. For race recommendations you can refer to this video.
Recommended potion for this build is an Essence of Health (tri-stat).
Recommended food for this build is Bewitched Sugar Skulls.
Recommended Mundus Stone is The Atronach.
For gameplay and the video showcasing this build, refer to the video above.