While you're walking around the Temple of Shar in Baldur's Gate 3 you might come across a small enclave containing some seemingly unnatural abominations and one necromancer in control of those abominations. His name is Balthazar, and he'll ask you to help him, but should you help him out?
Should you help Balthazar?
If you couldn't tell just by looking at him, Balthazar is one of the bad guys. He's the Necromancer for the overall villain of Act 2, Ketheric Thorm, and helping him is probably not advisable. Indeed, if you do help him then you'll cause Shadowheart to eventually become hostile towards you, giving into the poison of the Shadow Curse. This means that you can't progress her questline anymore, so if you like Shadowheart's story, don't help Balthazar.
All you can get if you help Balthazar is a bell that will summon the massive Flesh Golem named, fittingly enough, Flesh. You can also get a Moon lantern from him, but you'll probably already have one by this point.
Rather than helping out Balthazar, we'd recommend taking him out in this room specifically. If you wait until you reach the Nightsong then you're faced with a much more difficult fight overall, but attacking him here actually limits the potential he has to cause you trouble.
You see, keeping Balthazar alive until you reach the Nightsong themselves means that he'll go down there first and start talking with her. Once you approach him, he'll basically tell him your job is done and try to kill you by summoning a whole bunch of undead warriors. Unless you can counterspell his Raise Dead spell then this fight will be supremely tough since your party can be pushed off so many different elements of the map to their death. Better to get it over and done with as early as possible.