I've never actually seen them used this way, so I just want to make sure this is in fact a thing:
Unknown Nation searches your deck for a Human Evil Character to add to battle. Madness converts itself to an Evil Character and adds itself to battle. Since the only activation requirement is that there is a Hero in battle, can these be activated AFTER you've already presented a blocker and that blocker has been taken out? This was always my understanding of how The Gates of Hell worked, and the wording is the same.
Unknown Nation- Gold Curse, If opponent’s Hero is in battle, you may discard this card to search deck for a human Evil Character and add it to battle. Cannot be interrupted.
Madness- Orange Curse, If opponent’s Hero is in battle, you may convert this card to an orange brigade Evil Character and add it to battle. Cannot be interrupted.
The Gates of Hell- Evil Fortress, You may discard this card to add your demon to the battle.