Had a hard time finding info on the forums on Invasion 3. Managed to figure the following from youtube videos and trying it myself. Just putting down a miniguide for the noobs like me that have no clue.
Prep: I would say largely stack lightning resist first (as I don't know how to reliably avoid swirly lightning), then maybe fire resists (to survive long enough to run into blue circle).
These are the boss skills:
1) Swirly lightning (like invasion 1/2) - largely tankable/healable.
2) Lightning circle (like invasion 1/2) - summons a lightning bolt from sky within the circle after some delay. If you stand within circle when bolt lands, you are prob dead. This is the skill to dodge for the bonus quest.
3) Frozen shambler - randomly summons a frozen shambler and a blue circle. For the first 5 seconds after being summoned, boss emits a strong holy fire aura. Quickly run into the blue circle to become immune to the aura. Stay inside till circle disappears. Shambler itself does neglible attack damage
4) Nova attack - boss will become immune to damage (as your indicator) for a few seconds before this attack. Quickly run into melee range to avoid this attack. You can be lazy mode, and stand in melee range for most of the fight, and just run out of melee range when he uses lightning circle/summons shambler. But the videos I've seen, people just run around freely then blink towards boss when he 'charges up the attack'.
TLDR noob tactics: stack max light/fire res. avoid lightning circle. run into blue circle when shambler spawns. stand in melee range of boss.
For the pros - please add on. I sometimes randomly still die to the nova attack though I am in melee range. Maybe I'm just outside the safe zone. I'm sure people want to find the fastest/safest way to farm Invasion 3, to access labs.
Invasion 3 miniguide (for beginners like me)
Yeah there's more to know...
One guide (which has useful text describing the fight and strategy, instead of just a video) says that the cold circle is to avoid the fire damage that comes from the boss and it says you should watch his head and when... some red thing appears, go to the cold/blue circle to avoid the fire damage.
I watched the videos, same as you, and tried to copy but I still die to.. something. Tried hugging the boss, staying wide avoiding the lightning circles, I always run to the cold circle... still die. And this is Invasion 2 not even 3.
One guide (which has useful text describing the fight and strategy, instead of just a video) says that the cold circle is to avoid the fire damage that comes from the boss and it says you should watch his head and when... some red thing appears, go to the cold/blue circle to avoid the fire damage.
I watched the videos, same as you, and tried to copy but I still die to.. something. Tried hugging the boss, staying wide avoiding the lightning circles, I always run to the cold circle... still die. And this is Invasion 2 not even 3.
I saw some video of a paladin where a guy was standing in a corner all the time.
The biggest threat is this nova. Physical or magic? Shambler is for a few hits.
The biggest threat is this nova. Physical or magic? Shambler is for a few hits.
I finally completed the bonus quest for Invasion III and while I think it's a good fight, you can get screwed a lot by randomness. Sometimes the boss decides to cast his nova after spawning a shambler and you have no chance to avoid damage. Same with lightning circles, they can spawn all over the blue circle leaving you without a safe spot. I just kept retrying until everything aligned correctly. 
I think nova does magic damage, I tried with low physical resist and then with 50% + flat reduction, but it made no difference.
Yeah, that sounds correct, even if you kill the shambler and move out of blue circle you will take a ton of damage, which is the fire aura from the boss.
Immortal2563 wrote:I saw some video of a paladin where a guy was standing in a corner all the time.
The biggest threat is this nova. Physical or magic? Shambler is for a few hits.
I think nova does magic damage, I tried with low physical resist and then with 50% + flat reduction, but it made no difference.
Captcha wrote:Yeah there's more to know...
One guide (which has useful text describing the fight and strategy, instead of just a video) says that the cold circle is to avoid the fire damage that comes from the boss and it says you should watch his head and when... some red thing appears, go to the cold/blue circle to avoid the fire damage.
I watched the videos, same as you, and tried to copy but I still die to.. something. Tried hugging the boss, staying wide avoiding the lightning circles, I always run to the cold circle... still die. And this is Invasion 2 not even 3.
Yeah, that sounds correct, even if you kill the shambler and move out of blue circle you will take a ton of damage, which is the fire aura from the boss.
Oo thanks. I updated my miniguide info.
Btw I found that staying in melee range of boss is really the easiest way to go to avoid the novas. Alr got the bonus quest completed doing that.
Only thing that can go wrong is what someone mentioned and getting unlucky and boss stacks blue/lightning circles. You need fire res to just tank a few hits of the fire aura in those cases. Or unlucky with the nova attack after shambler spawns.
Btw I found that staying in melee range of boss is really the easiest way to go to avoid the novas. Alr got the bonus quest completed doing that.
Only thing that can go wrong is what someone mentioned and getting unlucky and boss stacks blue/lightning circles. You need fire res to just tank a few hits of the fire aura in those cases. Or unlucky with the nova attack after shambler spawns.
So I guess the summary is, stay in melee range, sprint out to wreck the shambler and get right back into melee range while dodging the occasional lightning bolt?
Yup I would say so. Running out is less to kill the shambler, more to avoid the fire aura damage.
Also to note, rarely but sometimes the shambler and circle will not spawn with the shambler in the center. It's a display bug and you should get in the habit of going to where the shambler spawned even if it's on the edge of what looks like the end of the blue circle, or even outside of it.
The boss gets icons above his head indicating the move he's about to do. Shambler spawn he does like a fireball helix animation that starts at his feet and then goes to his head and then a fire icon appears above his head, that means he's going summon a shambler (and towards the end I noticed it seemed to always be behind my character wherever that was, so maybe there's strategy in where you spawn the shambler).
Same thing for retaliate, except it will look like a cold spell above his head, he will go immune to damage and then send out the novas shortly after. You can avoid all damage by being next to/on top of him. If you have a blink(you should by the time you get to him) you want to save it for times when you're doing another mechanic and he does retaliate right after. For instance, I would be next to/killing a shambler and he would do the cold icon above his head and I would just teleport on top/next to him and eat the last couple ticks of fire damage instead of the entire nova. Additionally, if it's a bad overlap take a potion when you see the cold icon so you are having HP restored while taking damage from a nova or two, which could make all the difference. I don't think you can potion reliably if the retaliate is in the middle of going off but maybe you just need more FHR.
The boss gets icons above his head indicating the move he's about to do. Shambler spawn he does like a fireball helix animation that starts at his feet and then goes to his head and then a fire icon appears above his head, that means he's going summon a shambler (and towards the end I noticed it seemed to always be behind my character wherever that was, so maybe there's strategy in where you spawn the shambler).
Same thing for retaliate, except it will look like a cold spell above his head, he will go immune to damage and then send out the novas shortly after. You can avoid all damage by being next to/on top of him. If you have a blink(you should by the time you get to him) you want to save it for times when you're doing another mechanic and he does retaliate right after. For instance, I would be next to/killing a shambler and he would do the cold icon above his head and I would just teleport on top/next to him and eat the last couple ticks of fire damage instead of the entire nova. Additionally, if it's a bad overlap take a potion when you see the cold icon so you are having HP restored while taking damage from a nova or two, which could make all the difference. I don't think you can potion reliably if the retaliate is in the middle of going off but maybe you just need more FHR.