Every 2 casts, the Chronokeeper stores
1 XP. If he has enough stored for you to level up, he transfers you the required XP.
If you are level 10, he instead gains
15% Damage Amp.
Stored XP: 0<ShowIfCustom.Set=TFTSetEventCT>
In Choncc's Treasure, the amount of casts required to gain XP is increased to 3 until Stage 3-5.</ShowIfCustom.Set=TFTSetEventCT>