Been trying to kill this Mirelurk King as part of a quest.

[Loot]

Missed out on an Explosive Minigun because of it killing me the first time. Every time I get it to 5% HP, it instantly heals to full. I downed its HP bar 5 times in one fight and it healed to full every time. All the while, it's chasing me and fighting my companion and npcs in the area. It just needs one hit to kill me, but I've wasted hundreds of bullets with no effect. Are they supposed to keep healing to full, over and over? It's not Legendary.

[Castyles]

400+ hours on very hard and that never happened, here.

Are you running any mods?

[Loot]

Originally posted by Castyles:

400+ hours on very hard and that never happened, here.

Are you running any mods?

Yeah. I don't think any of them are supposed to cause that, though. If it's one of the mods, I have no idea which one it would be.

# Automatically generated by Vortex
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[The Inept European]

As a legendary it's supposed to regain its HP pool once, only. If it is happening more that once, not just when you reload and try again, that's a bug.

You will sometimes see humans use stimpacks but not creatures.

[Ommamar]

I saw something similar with a Behemoth. There was a Brotherhood of Steel chopper flying over the area that kept pulling it away from its spawn. It would get close to no health then randomly seem to heal to full health. What I think was happening was that the script was trying to reset it to its spawn point so when that happened it would get all its health back. Eventually the chopper crashed then I was able to kill it with the survivors of the BoS squad helping.
The only advice I could give is kill any of the NPCs fighting it as you can, it might get reset back to its spawn point. If it does at least your damage should remain with out its health getting reset.

[The Inept European]

There is the bloodbug bug where HP drops to near zero but won't go to actual zero/dead.

There is the bug where settlers take DoT and constantly die and get up again - both of these are vanilla bugs.

But I have never seen or heard anything like this one.

[Loot]

Originally posted by Ommamar:

I saw something similar with a Behemoth. There was a Brotherhood of Steel chopper flying over the area that kept pulling it away from its spawn. It would get close to no health then randomly seem to heal to full health. What I think was happening was that the script was trying to reset it to its spawn point so when that happened it would get all its health back. Eventually the chopper crashed then I was able to kill it with the survivors of the BoS squad helping.
The only advice I could give is kill any of the NPCs fighting it as you can, it might get reset back to its spawn point. If it does at least your damage should remain with out its health getting reset.

Yo, it moved from its original location, I think. That must be it.

[TheSuit]

There is a tendency for quest monsters to heal if they get pulled out of their quest area

[Loot]

I came back to it. It was still healing, but I was able to brute force it by killing it before it healed.

[tahunua]

I don't think I've ever encountered a quest where mirelurk kings are involved...

[Loot]

Originally posted by tahunua:

I don't think I've ever encountered a quest where mirelurk kings are involved...

It's a quest from the Gun For Hire mod.