Do lower level spells work against high level spellcasters?

Question

Last night my 10th level cleric was casting the wizard cantrip spell fire bolt against a high level cleric. The DM asked me what level spell it was and I said cantrip and he said it doesn't work.

I didn't argue his decision I just accepted it. I'm aware the intended target (high level cleric) could have cast a spell or had some magical item that could negate my fire bolt but not sure how the level of the spell matters. What should matter is the type of spell. But assuming the cleric did not cast a spell and was not using some magic item to negate my fire bolt should my fire bolt be effective against a high level spell caster? Assuming I hit of course.

Are high level spell casters immune to lower level spells? I can't find anything that says that other than higher level spell casters have higher saving throws. But in this case fire bolt only requires the cleric to roll a d20 attack roll and the intended target does not get any type of saving throw. So at a minimum if I were to roll a natural 20 I should have hit even if the intended target was a 20th level spell caster. Am I missing something?

Answer 1

There are a lot of reasons why a Fire Bolt could be guaranteed to fail. For example, the enemy could be immune to fire, or standing in an Antimagic Field, or behind a Wall of Force.

On the other hand, it sounds like the level of the spell was important. That narrows the list of potential options a long way.

• You may have been Counterspelled.
• The enemy could have had a Globe of Invulnerability.
• The enemy could have had an Ioun Stone of Absorption, an Ioun Stone of Greater Absorption, or a Rod of Absorption.
• The enemy could have been a Rakshasa in disguise.

There is not, however, any general mechanic which causes cantrips or other low level spells to automatically fail when used against high level spellcasters. High level spellcasters aren't automatically immune to low level spells, although they are more likely to be protected against them.

Finally, it's important to point out that the DM has effectively unlimited latitude in designing and using NPCs. If he decided that that character was simply immune to cantrips, then they would be. Your best recourse is just to ask your DM - if they want to keep their reasons a secret, they will, but they might be perfectly happy to explain their reasoning, too.