Overwhelming Spellcaster

Overwhelming Spellcaster
Prerequisite: Requires the ability to cast a spell

You may cast any spell using a higher level spell slot to increase the save DC by +1 for each level above the spell slot level required. Any time you are casting a spell at higher levels for added effect this feat is triggered and is added to the spell effect as well. Warlock spells that are upcast activate this feat as well.
In addition any spell upcast this way requires two successful saves or it is treated as a failure.
If you have the ability to cast tenth level or higher level spells you may upcast them as well to the limit your spellcasting allows.