The following actions require the PC to have a specific alignment, and will fail or produce undesired results otherwise.

Action Min Max Notes
Reading tome of donors Neutral Lawful Reading it while chaotic will also waste the try
Receiving Kill Riurry quest Neutral Lawful If the PC is chaotic Yrruir may be generated hostile
Receiving Hawkslayer as companion Neutral Lawful
Receiving quests from Ice queen Neutral Lawful
Receiving Courage quest Neutral Lawful
Receiving Healing skill from Jharod Neutral Lawful
Receiving Trident of the Red Rooster from Khelavaster Neutral Lawful
Receiving quests and services from Yergius Chaotic Neutral Yergius will still complain about being hungry to lawful PCs but will neither give his quest nor provide his services.
Receiving first quest from Gaab'Baay Chaotic Chaotic Once her first quest is received it's safe to change alignment
Receiving Rolf's Companion Lawful Lawful Neutral PCs receive alternate rewards, chaotic PCs receive nothing.
Receiving Rolf's Saviour Lawful Lawful Neutral or chaotic PCs receive alternate rewards.
Receiving quest from Rolf Race-dependent (Lawful for orcish, trollish or dark elven PCs; Chaotic for others) Lawful Non-lawful orc/troll/dark elf PCs will be attacked by Rolf instead.
Giving artifacts to demented ratling Chaotic Chaotic Demented ratling will devour artifact in either case. Be careful.
Giving corpses of chaotic beings to Guth'Alak Neutral Lawful Guth'Alak gives no reward to chaotic PCs.