One Save to Rule them All, Advantage by Class

XPLvl/HD        1        2        4        6        8        10        12       14        16        18...    
 BaseSave      16      15      14      13      12       11        10        9          8          7...    

Fighters

Advantage vs Mostly Dead Saves*, Poison/Venom, and Transformation Magic (Polymorph, Petrifaction, Withering)

*if using Death Save rules at negative HP

Magic Users

Advantage vs Spells, and most Magic Item effects

Clerics

Advantage vs all forms of Mental and Emotional influence or control, and vs magical Paralysis and Hold Spells

 
Thieves
Advantage vs Area Effects, Breath Weapons, and other Dodge-ables

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