Good Spell Save Dc
A spell s level can vary depending on your class.
Good spell save dc. Your spell attack is your intelligence modifier proficiency bonus. Spell save dc 8 your proficiency bonus your intelligence modifier. You could apply a negative save effect to the target s of the spell before the spell is cast or add a modifier to the modifier box again before the save is made.
At level 1 with a int of say 15 which mod is 2 you d have 8 2 2 12. For attack there isn t a base. There isn t a way to modify a spell save other than via the spell group dialog.
Saving throws in spell save dc. The ioun stone of mastery gives you 1 proficiency boosting your spell save dc to 27. The spell save dc is 8 proficiency bonus intelligence modifier.
Between 5 or 6 saves plus a couple of spells and the undeads there is no chance the paladin survives. For attack there isn t a base. For the dc to resist one of the spells equals 8 your regular spellcasting ability modifier your proficiency bonus any special modifiers.
But there isn t an effect which you can apply to the caster which would modify the casters save dc. If you want to be extra mean create big undead as suggested before but coat all their natural weapons with aboleth mucus and every first hit with the natural weapons force a fort save dc 20 or basically a death. This is a fantastic spell but your save dc probably isn t good enough for it to be reliable.
Always use the spell level applicable to your class. At level 1 with a int of say 15 which mod is 2 you d have 8 2 2 12. A saving throw against your spell has a dc of 10 the level of the spell your bonus for the relevant ability intelligence for a wizard charisma for a sorcerer or bard or wisdom for a cleric druid paladin or ranger.