How much Damage would a Lightsaber do in D and D?

[The Rose Dragon]

If you want a G-canon character, not force-sensitive, who is able to wield a lightsaber in battle without damaging himself- how about General Grievous?

To be fair to Grievous, he was a cyborg and probably had preternaturally fast reflexes that allowed him to wield the lightsabers without harm.