D&D 5E Is Rime of the Frostmaiden the deadliest 5e campaign (probable spoilers)?

[Paul Farquhar]

But if you realize it's ice, it's a pretty obvious second weapon to try once the first one fails to do any damage to it.

A huge proportion of things in RotFM are either vulnerable to fire or resistant to stuff that isn't fire. If you haven't learned to make fire your first-choice weapon you haven't been paying attention.