A delayed effect has yet to fail me, but neither am I sure about them. I'd like to hear some awful campfire stories about effects not applying, not persisting in saved games or their timers thrown off by map travel... Give me goosebumps.
Damage and damage resistance behave differently depending on when and how they are applied, resulting in delayed damage sometimes ignoring the targets resistance to it.
The "Source" of an effect is not saved if you save/load, at least for the purposes of targeting.
The available delayed timing modes are all "limited" timing modes, in that they are removed by Death, Exportation, Pre-generation, and Opcode 17(w/Bit 17 checked). They are not however removed through level-up or dual-classing.
The creature that cast/activated the spell/ability. For example, targeting modes "Self(1)" and "Original Caster(9)" don't always work correctly if you save/load between the effect getting processed.
I'm going to have to look into that, for sure. I've used a Self-targeted filtered effect through resting at an inn and map travel, and it kept the right probabilities, but I haven't tried saving. Then again, there has been an autosave or even a few in between. Or do I have to load the save for the effect to be thrown off?
I've only had one problem with delayed effects: they don't change their duration when the character has an effect that changes spell durations. So if you have something that doubles your mage spell durations and you cast Spirit Armor, the AC bonus will last for double the time, but the delay until the character takes the damage doesn't change.
Theoretically couldn't some fixed feature be used as a memory aid for the game? If the engine forgets what the level or statistics of the caster were on loading, might it not be made to look at something that won't change, like an item on invisible creature, spawned immediately with a timer? Timers don't get screwed up with loading too, do they?
Here is another thing. Marek and Lothander in BG:EE. They are the assassins of the Iron Throne who meet the party in Baldur's Gate, and Marek poisons the party. This begins the quest for an antidote. Now, I haven't looked into how it works, yet, but if this is a delayed spell effect, then it would be thrown off by a save-load, yes? Doesn't seem to be the case, or it would be an awfully easy way to detox.
Here is another thing. Marek and Lothander in BG:EE. They are the assassins of the Iron Throne who meet the party in Baldur's Gate, and Marek poisons the party. This begins the quest for an antidote. Now, I haven't looked into how it works, yet, but if this is a delayed spell effect, then it would be thrown off by a save-load, yes? Doesn't seem to be the case, or it would be an awfully easy way to detox.
I'm sorry to destroy your dreams but the quest is tracked by a global variable and baldur.bcs probably, and it just uses a script to genocide your party (probably baldur.bcs again). No delayed spells involved AFAIK.
Comments
The "Source" of an effect is not saved if you save/load, at least for the purposes of targeting.
The available delayed timing modes are all "limited" timing modes, in that they are removed by Death, Exportation, Pre-generation, and Opcode 17(w/Bit 17 checked). They are not however removed through level-up or dual-classing.