Has anyone been able to beat the boss?

Cuz I've had 7-8 people assist from the blue grave and every one of them died within 1 minute. I mean they really got beaten down fast.

Why would someone put a blue grave down by that boss if they suck a lot worse than me at the boss?

The NPC AI is just not good enough for bosses and dies too quickly. If you're summoning blue graves, pick spear users as they will have larger pools of health.
If you're struggling with the boss we have text and video tips on the [url-https://nioh2.wiki.fextralife.com/Enenra]Enenra[/url] page.

Ok. How do I find a blue grave of an actual person?

To summon a real person you need to offer Ochoko cups at the shrine under the "summon visitor" menu

Information on online can be found on the Multiplayer page on the wiki

If you want write to me on ps I will help you

You can bait him into destroying the pillars which douses him in water giving you a boost. I'd avoid attacking him during the Yokai Realm phase. Dodge the tornadoes and try and bait him into a "red" attack, then Burst Counter and follow up with several attacks.