This concept isn't very complete, I highly suggest you put some more effort into this. A name is practically mandatory and you skipped that step. No lore, no art, no description of abilities or character, no quotes, no gameplay notes, no explanations, and no formatting. I highly suggest you put a little more work to develop your concepts.
For this concept, I think it would be sort of toxic. The passive is pure luck, it requires no skill and you can't control it. It would feel really bad for you if the % chance didn't save you but really bad for the enemy if it did. Also, the % increased damage to explosions should be removed. Then you get into nitpicks like "Is Brand's W considered an explosion or just fire being molded into a shape?". Additionally, real life logic shouldn't apply in League of Legends because we have little girls throwing fire and little sad kid mummies. And, it doesn't feel very fun in the game when Nami does increased damage to Brand just because she picked Nami. League isn't a game of rock paper scissors.
Golem's Q ability is literally just malphite's E without the attack speed slow.
W is interesting in concept but you fail on delivering. Its just a boring minion that you can't control and has minimal interaction. Additionally, this ability would possibly be considered toxic, leading for this champion to be nerfed heavily like old Yorick. This W functions very similar to old Yorick's ghouls and that wasn't a fun experience at all.
Golem's E is ok, nothing special or unique but it functions.
Now Golem's ultimate feels really bad to use. Due to the fact Golem has to wait 50 seconds just to get 5 mini golems. Now that Golem has 5 mini golems he can finally get the most out of his ultimate... oh wait the enemy just killed them and now he has to wait if he wants to use his ultimate and have any worth out of it. Additionally, this ability just feels terrible if you don't have enough mini golems. And due to the fact you have no control over when and where mini golems spawn, it feels even worse as an ability.
Finally, Golem's ultimate, Unstoppable Force, has the same name as Malphite's ultimate Unstoppable Force. Golem's ultimate however feels like an extension of his W. It doesn't feel like an ability on its own, it feels like an extension of Golem's W.
Overall, this concept currently is too similar to Malphite. They're both big rock monsters, with Unstoppable Force as they're ultimate names, both with a big AoE grand slam, and both counter AD champions. However, Golem would never be picked due to the fact that he is just a big meat sack. He is literally a meat shield for his team that brings some damage but his damage is incredibly unreliable and he has no crowd control like a stun or knock up.
So you should work on this:
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Format and complete your champion concept more.
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Differentiate him from Malphite. Make him unique.
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Rename his E and Ult, those ability names are already in the game.
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Give him some interesting ability that you've never seen before in league.
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And give him some crowd control.
