@JeremyECrawford Spell Thief feature lets you force a saving throw with spellcasting ability mod. Is it considered to be the same kind of ST as the modifier? For example, if the creature use int mod for spells,Is it a Int save? I ask because of proficiency bonus.

— Ironforged (@TrueIronforged) November 22, 2017

If you make a saving throw using a particular ability modifier, you're making a saving throw using that modifier's ability. For example, an Intelligence saving throw is a save that uses your Intelligence modifier. See "Saving Throws" (PH, 179). #DnD https://t.co/TM74CtVyPu

— Jeremy Crawford (@JeremyECrawford) November 22, 2017

Okay, so a int save uses int modifier and any save using the int modifier is an int save.Yes.

— Jeremy Crawford (@JeremyECrawford) November 22, 2017