The level (and HP/damage) of your King Tower, and the level cap that Card Boost Potions and some features reference. Now determined by how many cards you've upgraded to given levels rather than by XP.
Since the 2026-05-26 update, King Tower Level only stays the same or rises and is no longer driven by Experience/XP. Max is Level 16 (Ranked stayed capped at Level 15 until May 2026).
