Flex
Flex grants Strength for the turn, then removes that granted amount at turn end; its upgrade doubles the listed amounts.
How it works
The base text grants 2 Strength and says to lose 2 Strength at the end of the turn. The upgraded text grants 4 Strength and loses 4 at turn end. The card list identifies Flex as a Common Ironclad Skill. It does not describe additional duration or interactions.
Read the supporting references
A focused reference to ten Ironclad cards and their recorded effects, including listed upgrades and play conditions. Card details come only from the retrieved Slay the Spire 1 card-list passage. This does not attempt a complete card, relic, character-unlock, or Ascension guide. Guidance explains the referenced mechanics; it is not a tested damage ranking. Check the stated edition and source version before applying a patch-specific detail.