u/MadAnonimusi

So difference between those 2 items are that Axiom is 50 gold cheaper, 5 more haste but 5 less AD.

Axiom allows you to have your ult active more often due to its passive, while Umbral lets you clear wards and thus flank or make picks easier and gives you about 75 true damage on first basic against champions

Only thing I can think of why they go Umbral is because vision must be really broken in high elo? Id say having your ult up trough the game is stronger but idk, what do you think?