Note that this relic can remove the debuffs inflicted on yourself via certain cards, such as Biased Cognition and Wraith Form; this can make such cards far more valuable. Flex also works via a debuff and will provide strength for the rest of the combat if it can be removed that turn. The same goes for Speed and Flex potion.
Related to the above, the Confused debuff that is inflicted by the Snecko Eye relic will be removed, but the bonus card draw will remain active.
If the last card played to activate this relic applies a debuff, that debuff will be removed. Debuffs from a second play (such as those enabled by the Necronomicon), however, will remain.
If you use this to remove Confused, cards will retain their current costs for the rest of combat.