How many Demonic Core Essences are needed to advance in rank in "No Rest for the Wicked Quest"? And what are the benefits?

Question

No Rest for the Wicked Quest has a rank system and it's possible to advance in rank by delivering Demonic Core Essences to NPC Lai. After delivering 100 essences and reaching rank 1, we can use the essences to advance in rank, without needing to run back to Lai.

What is the highest rank I can reach? How many essences do I need to deliver/use to reach each rank? And what are the benefits of advancing in rank?

Comments

To whoever flagged my question: please read everything before reporting. My question is totally different!

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I removed the flag and agree

Answer 1

Extracted from the wiki:
You'll receive agony damage equal to 5% of your max hp every 20 secs
 

Rank 1	Cores 100	Access to the first three floors in the Catacombs	Damage reduction 4.5%
2	200		4.0%
3	400		3.5%
4	800		3.0%
5	1,600	Access to the last floor in the Catacombs	2.5%
6	3,200		2.0%
7	6,400		1.5%
8	12,800		1.0%
9	25,600		0.5%
10	51,200	Tear the Toxic Veil achievement	0.0%

Comments

If I remember correctly, during the test server it was possible to access the first 3 floors of the catacombs without handing over the 100 essences. Can anyone confirm this?

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Yes, during the test server the first 3 floor were available for free

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If this hasn't changed after the update, it would be a good idea to correct this information in your answer