Foehammer Trophy in Baldur's Gate 3

• You get one save slot, which the game overwrites. You cannot reload.
• If the whole party dies, the Honour Mode run ends.
• Bosses have legendary actions, extra moves they make during your turns.

What helps:

• Examine every boss before the fight to read its legendary action, and plan around it.
• Win initiative. The Alert feat and an Elixir of Vigilance both help, and so does high Dexterity.
• Keep invisibility scrolls or spells on everyone, so you can get a character out of danger.
• Skip optional fights you are not sure of. If a fight is going badly, run back to camp and pay Withers, the skeleton there, to revive anyone who died.
• Use what you learned on Tactician: the same tactics work, with no room for mistakes.