What I have learned is that your role is more important than class and that each class doesn't have to be true to type. Not sure how to play a Nightblade though. Not really my cup of tea.

Well, so far, I´m on level 7 and using only two abilities. It feels more like Orc warrior-warlock to me right now  It´s really overwhelming for me, especially because it´s much different than WoW or SW:TOR

It's like a whole new language too, one that MMO guys are fluent in. They shit in their socks so who gives a fuck?

Don't forget your other skills, your racial line and weapon/armour lines. Also, crafting is best started early with a research on the go at all times if you are interested in such things. Store all your crafting stuff in a bank.

The reason why I´m using only two-three abilities is because I´m not forgeting the Orc skill line (which seems really great for a tank) and heavy armor skills. I have only one point in shield, but that´s going to change very soon.

From my experience as a Nightblade tank, you'll want to run weapon and shield and either Medium or Heavy armour (or both). Medium gives you some nice evasion options if that's your deal.

As for abilities, you can mix and match for what suits you but my main abilities were:

• Aspect of Terror->Mass Hysteria - Good for getting guys off your allies for a few seconds
• Assassin's Blade->Killers Blade - Good for keeping your health up on little guys and finishing off bosses
• Teleport Strike->Lotus Fan - Use to move to groups of enemies or allies that are under attack. Also an AOE snare which is also welcome
• Strife->Swallow Soul - Tag each enemy with this at the start of the fight for some damage over time and heals. This  morph also increases your healing received which is very important.
• Siphoning Strikes->Leeching Strikes - Restore health, magicka and stamina with basic attacks! Wooo!
• Puncture - You usually need a taunt to tank effectively
• Defensive Posture - Very useful on some bosses but I usually don't bother

Overall I found NB tanking to be mostly about regeneration rather than avoiding damage. You'll be quite magicka heavy so invest most points in Health and Magicka. Stamina is still used to sprint, block, dodge and taunt so don't completely neglect it!

Thanks, Ponty. I already took the Swallow Soul, and Puncture. So I should take some Assassin and Shadow abilities too? Alright.

And please tell me there´s an option to reset skills.

Yep, in your faction's second zone there's a respec shrine in the main town. You've got options to respec all skill points or just morphs.

Hm. Guess I´ll have to drop the Orsinium for now and continue the Faction quests.

Thank you, Ponty. You´ve helped me a ton.

So, I´ve run through my first dungeon and I have to say...I´m not sure if I was good tank or not  One thing I know is that AoE aggro is real problem for me right now, I was taunting as many mobs as I could, I managed to dodge whatever "red" they´ve thrown at me, but what I really fail to do is block and interrupt in the right moment. For some reason, I just don´t register what those mobs (bosses are quite ok) do, especially when there´s like 7 of them. 

Good thing is, only 1 guy died in that dungeon - not sure if that´s my work or good healer...

So, how do you keep aggro on multiple mobs with Nightblade, Ponty? I´ve morphed the Teleport strike to do aoe damage, but that DoT doesn´t really help with immediate aggro. I feel really overwhelmed in this moment, but to be honest, I thought it would be wipe run with me as a tank. It wasn´t really a disaster, but I feel I could have done better.

Keep in mind in dungeons you can let your DPS deal with some of the regular mobs - tanking in ESO your main concern is to stop the more dangerous ones (like bosses, hard hitting melee guys, or anyone else with a dangerous ability) from being a threat to the rest of the party. Nobody has an AoE taunt but usually tanking involves lots of snares and similar abilities. Lotus Fan is good for this since you can dash in to groups of melee mobs and snare them, giving your DPS time to back up or mop them up. Starting out this can be tough but once you get the Fear ability it becomes much easier.

Unlike a lot of other MMOs you don't need to be holding aggro from absolutely everything to be an effective tank. I wouldn't worry about it too much, to be honest I was in a similar situation to you starting out as a NB tank, but most of their good abilities come later on. See how you go in your next dungeon and if you don't like it you can always respec - Nightblades can also make excellent beefy melee DPS characters!