More Useful Intelligence (5e Variant Rule)
From D&D Wiki
This variant rule intends to make Intelligence a more worthwhile investment for characters who don't have it as a casting ability, and give some mechanical justification for not always making Intelligence your dump stat.
Under this rule, the amount of skill proficiencies a player-character is granted from his or her class is reduced by one; except for the wizard class, which under this rule grants no inherent skill proficiencies.
A character can gain additional skill proficiencies from his or her class's skill list at Intelligence score thresholds listed in the following table. (A multiclassing character only gains additional skill proficiencies from his or her first class.) A permanent increase to Intelligence can grant an additional skill proficiency.
- A character with 7 Intelligence or lower can't read or write any languages, unless the character forgoes gaining a skill proficiency to learn to do so, or its Intelligence increases to 8 or higher.
- A character with 13 Intelligence or higher can freely learn any one additional language (excluding any secret language, such as Druidic).