If my character is a spell caster, and he is not wearing any armor, is there any chance to fail casting the spell? I'm wondering specifically about normal circumstances: There is nobody who can attack him, and nothing which can interrupt him. Is there a check under normal circumstances to successfully cast the spell — maybe a Spellcraft check?
I ask because it's a little weird to me that a spell caster in normal conditions would have a 100% chance to cast a spell.
Best Answer
No, not generally. Spellcasting in D&D or Pathfinder is a routine process -- you select the spell, and then cast it. The character is presumed to be so proficient at this process that there is no chance of failure under normal circumstances.
However, there are some special cases where there is a chance of failure. Two of them require the caster to make a check on a d20 to succeed.
Concentration checks: When something distracts you from casting the spell, you must make a concentration check or lose the spell. Taking damage or choosing to cast defensively are the most common types of distraction, but strong weather, casting from horseback, and several other conditions will also require this type of check.
Spell Resistance: Some creatures have resistance to magic. This can be overcome by making a caster level check. Failure does not cancel the spell, but does prevent the creature from being directly affected.
There are other chances of failures that aren't really "checks", but I thought might be worth mentioning.
Arcane spell failure: Arcane spells which have somatic components can be tricky to cast while wearing armor; there will be a flat % chance of losing the spell. This chance is determined by the type of armor (and shield).
Deafness: A spellcaster who cannot hear has a flat 20% chance of ruining any spell with a verbal component.
Incorporeal creatures: A spell which does damage deals 50% of that damage to an incorporeal creature, but other types of spells simply have a 50% chance of failing to affect them. (Force spells and channel energy have full effect.)
Finally, it is worth including the one additional case where you do have to make a check to cast a spell.