About this

In general, it's not a bad idea to make the bosses in Minecraft have a health bar that the player or players can track. And Warden, he's weak. He will be locked in a box of blocks and will not do anything to the player. And let him be able to dig into blocks infected with a sculk and move and then reappear and continue to look for his prey.
Add monsters around the Ancient City. For example, a zombie infected with a sculk . How did it happen, before the zombie was a jock and suddenly he was surrounded by a crowd of zombies and a bite. So he became a zombie, but unlike others, he is more resilient and stronger. A zombie jock was walking and saw the Ancient City. And he got infected with a sculk. Ordinary ones would immediately disappear and turn into sculk blocks. And he got stronger.
About drop... enchantment books that are... infected with a sculk. heh