NHF – new heroes for Heroes V 3.1.

I think it's interesting. Like a "trickster out of the box."
But it needs to be modified: he should be resurrected not with a portion of his army, but with a new army (depending on his level). With something useful for the trickster – ghosts, for example. And an unlimited number of times. That is, to get rid of him, you need to deprive him of cities; otherwise, there's no way. That's it, he's a good guy right away.)
As an additional option: resurrect the hero immediately in the garrison of the nearest city. Then any siege is two battles in a row with this hero (outside and inside). Maybe it's a bit too annoying, though.)

Yeah, it's very annoying :) An unlimited number of times is too overpowered. You can easily level this hero up to level 40 because he won't lose anything.
Let's do this: each time he is resurrected, his level and stats will be halved. Let's call his special ability "Immortal." I think he should be given protection with "Fight to the Last" and maybe a summon.
The description could be something like this: "During the War of the Broken Staff, when the mages advanced on Erathia, he defended an important garrison on the approaches to Nar-Erish. His army was defeated, and he himself was surrounded. At the last moment, he managed to raise some undead and fled to Nar-Erish, where, together with other necromancers, he was able to repel the attack of the mages. After this incident, he was nicknamed the Immortal."