From the Kingdom Hearts Wiki: A world of information not accessible by Gummiship
In Kingdom Hearts Union χ, Blaze Slash is a special attack that targets random enemies. It costs 3 special attack gauges to perform. It deals exceptionally powerful hits. It raises either the player's Power-, Speed-, or Magic-based strength by 5 tiers for 1 turn, depending on the Medal's attribute.
Learning Blaze Slash
Kingdoom Hearts Union χ