Created a 11 Arcane Trickster, 9 Gloom Stalker.

When scrolling through spells, the DC saves are all WIS based even though my Rogue spells use INT.

i.e. Fear Spell DC: WIS 19, Mind Spike Spell DC: WIS 17. 

My spellcasting ability for WIS = 19 while INT = 17.

https://ddb.ac/characters/22322143/2q1Zm7

It's because your character is multiclass and the spell save DC is determined by which spell list the spell comes from

Your range spell save DC is 19 and your rogue DC is 17.

Fear is a ranger spell so it uses the ranger DC of 19

Mind Spike is a rogue spell so it uses the rogue DC of 17

Also, the Ability Score listed by the DC save in the Spells section of your sheet is the type of save the target must make, not the ability score used to determine the DC #.  Mind spike, for example, requires the target to make of wisdom saving throw. This is true regardless of what class of caster casts the spell.  But the DC is (correctly) being based on your rogue DC#

I obviously made a few assumptions about spell casting ability being linked to the type of save a player has to make. 

Thanks for clearing that up! 

Quote from LeonD1511 >>

 

I obviously made a few assumptions about spell casting ability being linked to the type of save a player has to make. 

Thanks for clearing that up! 

 The type of save the target makes is independent of you the ability score used to determine the DC. A bard and a wizard can both cast fireball, and the save will always be Dex, but for a bard the DC will be determined by charisma and for the wizard, it'll be based on intelligence.