What is the highest tier

Is tier 16 the unique items is the highest ?

Yes, but u can upgrade it's tier to 17 (mb more I dunno)

What? Explain further

U have 16 tier item -> use option "tier upgrade" -> get tier 17 item with same stats, except base armour or dmg or all resists (these three will be increase).

OK ....how come other players level 50 and below have a billion attack and defense ....it's impossible ...do u think its a cheat....just asking.