Why was banner removed?

Because Banner became one of the largest meta-shifting items in the game?

What is most likely happening is they are going to overall how minions perform, maybe a minion controlling champion, maybe a champion who can convert enemy minions, etc. and having the ability to uber up a minion, just breaks balancing that kinda thing.

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But Ohmwrecker still exists? There is legit no reason to ever buy the item other than for shits and giggles.

Don't git it.

because they made two changes and they both failed so they real issted of taken time to work on it they will just remove it

Banner is either useless or meta-warping. Ohmwrecker is just useless.

Same reason Boot enchantments are gone. Riot gave up trying to balance it.