INT = ability to out-think enemies
High INT = Discredit Attacks
Smart Creatures can attack the opposing Narrative and Groups.
INT 8 or higher = creature may perform a Discredit attack. Creatures affected by summoning sickness cannot Discredit.
High INT = Protects Against Some Targeted Effects
Some effects can only target vulnerable Creatures with low INT.
Example: Panopticon You which has the rules text:
This Skill equips for a 1F cost to an opposing active Creature with INT below 7.
INT stat - even more important for Figureheads
You should pay closer attention to the INT stat on your Figurehead Creatures, since they are able to use the Fundraise action if seated, which awards Funding to the player depending on the INT value of that seated creature.