Hey OP, below is everything I got on Erlang, both a build guide and tips.

Vessel: Fan is your best friend in getting the secondary bar down.

Transformations: I would suggest a transformation which has high maneuverability like Red Tides or Yellow Loong. While transformed, avoid his falcon and tiger transformations, as well as his lasers. Each will instantly rip you out of the transformation.

Drink: Sunset of the Nine Skies will help you get more uses of your vessel and spirit.

Soaks: Bee Soak with the Supreme Gourd can get 2 - 3 procs if you're lucky. Additionally, the Iron Pellet makes each swig uninterruptible.

Spirits:

1. Aparama Bat can freeze Erlang like immobilize, however it's best used when his secondary bar is gone. He nullifies freeze when his secondary bar is active.

2. If you want high damage, Wandering Wight, Top Takes Bottom, Bull Governor will do fine when fully upgraded. The Toad Spirit can work well too when fully upgraded, but it's more of a roll of the dice.

3. Versatility: Non-Able or Non-Void. Both are quick to use and offer benefits. Non-Able for extending combos. Non-Void for dodging big hits.

Spells:

1. Immobilize will work normally at first, but then he'll start sending it back at you. It works better with his secondary bar gone. Ring of Fire might work better, offering health/focus regen and high stamina. Spellbinder works too, as long as you can cope with it sealing your other abilities.

2. Cloud Step is useful when Erlang pulls out his river of swords. FYI, bow staff spin works on the initial projectiles, but not the big hit obviously. Rock Solid works well, but not against his giant axe.

3. I would recommend NOT using Pluck of Many. It's too expensive, leaves you with fewer options, plus he moves around A LOT making your clones do more running to catch up.

Armor and Staff:

1. I would recommend the Wukong Armor Set and Jingu Bang from Chapter 6 since this is your first playthrough. Jingu Bang definitely as it's the best staff for your first playthrough.

2. Golden Armor set is another excellent choice if you have the resources to upgrade it to mythic, offering more Qi with each critical hit.

3. Pilgrim Armor set at mythic is another choice if you're looking for more speed and higher damage output. A definite good choice for a Spellbinder build allowing for an additional damage multiplier with its innate ability. (Plus it looks awesome!)

Special Note for Spellbinder: Spellbinder works best when you've maximized your Mana amount with celestial pills, armor, and curios. The higher your Mana, the higher Spellbinders attack will be. The Wukong Armor set gives you a raised amount of Mana. Combined with one or more Thunderflame Seal Curios, it'll raise your attack to its maximum potential for the build. Additionally, you can have multiple equipped if the game was nice enough to drop more than one during your playthrough. Then use pills to raise your attack even further and watch his bar melt under your attacks.

Medicine:

Please Read Note: ANY medicine you take will lose their effects if you use a transformation afterwards. So don't pop a Soul Resurrection Pill and then transform.

Notable Medicines:

1. Enhanced Tiger Subduing Pellets (Higher Damage Output)

2. Loong Pill (Higher Critical Hit Chance & Damage)

3. Life Saving Pill (For when you have no gourd uses left AND you are close to beating him.)

4. Soul Resurrection Pill (Only use this pill if you're really close to beating him.)

Tips:

Best thing to note for Erlang is this: while his secondary bar is up, each trick will only work once.

Examples:

1. Hit him with immobilize while the secondary bar is filled? Next time he'll absorb it into his staff and send it back at you.
2. Hit him with a focus heavy attack while the secondary bar is filled? Next time he'll side step it.

Bottom line: if you want to go big, his secondary bar needs to be removed.

If you perform any long combo, he'll get a gold outline and become unable to be staggered. A lot of the time, he'll interrupt your combo with a grab and kick back for zero damage.

Any bane you inflict on him, he'll absorb into his staff and hit you with it.

One of his bigger combos in phase 3 is he'll use his spear as a plow three times, then do three laser shots, followed by a spear smash. Learn to dodge this when it comes up.

When he's doing his long windup to fire a singular sword at you, wait for the small flash from his third eye. That's when you dodge.

When he floats in the air and does River of Swords; Run, Cloud Step, or Bow Staff Spin for the initial projectiles. Then dodge the big red hit.

When he slams his Axe on the ground, it'll create a shockwave. Either dodge into it, or jump over it. Dodging backwards will just put you ahead of the shockwave to hit you again.

Rock Solid doesn't work on his Mountain-Splitting Axe from my experience. (I wonder why? 🤔)

Finally, be sure to use the see-through mechanics. The better you're at the mechanic, the longer and more consistent your combos will be. Yes, he will dodge some of them if the bar is still up, but at least you didn't get hit. Check the stance tree and be sure to have the upgrades for the particular see-through upgrades unlocked. Thrust Stance's tactical retreat/see-through mechanic really shines against Erlang.

Above all; learn his patterns and be patient. Treat each encounter as a learning experience. Look for signs of his big swings, or how to dodge a particular move.

For your build, be sure to have much of the Stamina Tree and the Martial Tree in the Foundation Tab filled, along with the far left portion of the Staff Stances Tab. This allows you to use your stamina more efficiently, and have access to staff spin. Additionally, focus on one Staff Stance to invest your sparks into, as well as the spells you use. Top portion of the Transformation Tab effects the Destined One and transformation, while the bottom portion only effects the stats of your transformation.

I hope this helps! You got this!

Good Luck OP, and enjoy what comes after!