Somewhat got inspired by Roblox Grace to come up with the idea of "Chronicles" that are basically just a unique take on boss battles for certain enemies.
The basic premise is a moon you would land on that would house each "Chronicle" or boss. A player goes to a giant terminal and browses their bestiary logs to choose which battle to begin. Once chosen, the screen would crack open and flood the room with light, teleporting players into the battlefield.
Each area would feature a special collection of progressing mechanics in a unique "arena." Instead of attacking the enemies directly, each battle consists of these mechanics and gimmicks that attack their "memory," logged into their minds by Sigurd's ramblings.
Stamina is kept permanently maxed out and speed is increased.