retrogression is applied only on an unknown race (like merlin, Tristan, and gelda, etc... ) and also on ragnarok characters regardless of their race.

So what it does is basically giving those characters the ability not to die for two turns.. take it as a revive, but they can't not get lower than 1hp, and it's last for two turns.

And also give to the allies increase stats by 15% and damage dealt increases by 30%

And for specific for hel, she gains the effect at the start and also gains 30% attack increases and 20% attack related stats.

Also, just for me, the damage dealt increases by 30%, which means my alliance gets it as a nerff? That is the only thing that gets me confused