What is the meaning of this!?!?

Crasyduck

I just want to r4 my sentinel but...

Why would they do this?

Deacon

it's been like that since Variants first appeared. the rank up gems (outside of the 4-5) have always been specific to years.

Mr_Predictor

It's a 2016 gem. Sentinel was released too late to meet the requirements.

Crasyduck

Man, that stinks

Demonzfyre

I'll never understand why people are surprised about these gems. Each variant announcement this is explained in the main thread. You can also click on the image in the rewards screen it says it's a 2016 gem. When you click on the gem in your inventory, it lists exactly what champs it's good for. If they aren't listed, it can't be used on them. It's really simple.

Kabam Zibiit

Hey there, you can reach to our Support Team to get some assistance with that. You can reach them from the game's home screen by clicking the gear-shaped icon in the top-left corner of the screen and then scrolling down to the button labeled "Support".