DC Measuring Contest

You force a target within range to undergo a DC measuring contest with you. Choose at the time of casting whether you wish to attempt to charm or frighten your target. If your selected target does not have any spells, actions, or abilities that force a saving throw, the spell ends immediately. If the target has at least one spell, action, or ability that forces a saving throw, you learn the highest DC in your target's arsenal. If your own spell save DC is larger than that of the target's DC they become charmed by, or frightened of you for the duration of this spell, or until your concentration drops. If their DC is equal to yours, and the target is hostile to you, the creature is no longer hostile to you, and this casting of the spell no longer requires concentration, as mutual respect for the size and girth of one another's DCs breeds in both you and the target a sense of mutual respect. (This creature may become hostile to you again if you or a party member takes any actions that the DM deems a large enough argravant to the target, but the target will otherwise remain non-hostile even after the normal duration of this spell. This loss of hostility might not extend to your allies if the DM deems it so.) If the target's DC is greater than yours, you lose concentration, and you become frightened of, or charmed by the target of the spell for 1 minute, or until you are relieved of the condition by the effects of a spell (such as Calm Emotions), or another such ability that can end the condition placed upon you. Which condition is applied to you is decided by the choice you made when the spell was initially cast.

At higher levels: You may subject one more creature to the effects of this spell for each spell level above third. If you do so, each creature including the caster becomes frightened of or charmed by only the creature or creatures with the largest DC (negating the loss of concentration for a tie at the highest DC, unless every creature affected including the caster has the same DC).

"I'll show you mine if you show me yours."