my bard wants to take simulacrum and Wish as his magic secrets. An army of Bards non the less I have been trying to come up with ways to make this work.... I also wanted ways to counter this, after long out of game talks on it lots of hours. I have noticed that he just wants to be super OP and walk over everything i really think this is gonna kill the vibe of the campaign. So i then tried to talk him out of wanting to take it, offered a respec of those magic secrets etc. He was gotten lets say Verbally Violent. his nickname is Mr. Raw given to him by the other players, he honestly relishes in it.  "its a spell in the game i can do it if i want" blah blah blah kind of stuff. Not a DM that likes to say no i love to try to make it fun for everyone. So im trying to think of ways to counter it. PHB has a section labeled "The Weave of Magic", what is the effect of breaking the weave? Certainly casting wish hundreds of times in an area for days upon days has to have some kind of Black hole atomic bomb destruction explosion right? Jk on that last part.... kinda.... ive only been a DM for a year and a half. any ideas for me guys?

Honestly the effects of that are up to you. Maybe the goddess of magic doesn't like having it happen? Maybe the player character forgets which one of them is the primary one? Maybe the Wish bypasses any proxies casting and still effects him because the simulacrums are an extension of his magic? Maybe he cant afford to do it because the component cost for simulacrum is a lot, especially for multiple. Maybe he cant do it because "If you cast this spell again, any currently active duplicates you created with this spell are instantly destroyed."

Frankly, I like the idea of the magical singularity that causes wild magic surges and ultimately an anti-magic zone that forms around him, making him unable to regain spell slots until the anomaly is dissolved.

Edit: I also like the idea that, somewhere along the chain of command the simulacrum stop listening to the bard because of how far removed he is from being in control. They could start casting wish to, say, become a real person, or become the new leader, or to negate all other wish spells because there can only be one prime. 

We'll assume 20th level : 2x 7th level slots, 1x 8th and 1x 9th. Just so we can see how this goes.

PC uses 7th Level slot to cast Simulacrum to make a simulacrum of themselves, we'll call Sim 1.

Sim 1 uses its remaining 7th level slot to cast Simulacrum to make a simulacrum of PC, we'll call Sim 2.

And so we have the daisy chain. Each Sim is a copy of the PC so each Sim has a 7th and 8th level spell slot they can use for casting Simulacrum. They have a 9th they can use for casting Wish.

Each Sim costs 1,500 GP to make. If they run out, well, they can have Sims start using Wish to replicate the Simulacrum spell without needing material components.

Each Sim will obey the one that made it and those instructions can include obeying the PC.

This is permitted by RAW.

If you do not like this you have options to prevent it:

• Ban the Simulacrum spell. You're the DM, you have say over what spells are available or not.
• Rule that a creature can only be the target of one casting of the Simulacrum spell at a time.
• Rule that a Simulacrum cannot cast the spell Simulacrum (not even replicating it via Wish).

You could impose the rule as a DM direct ruling or you can invent an in-game reason behind these.

You could also choose to allow it but provide in-game consequences: the PC has drawn the attention of other mages - perhaps one who has already been doing this very same thing and so decides to send their army of powerful mage Sims against the PC to prevent their rising power and keep such a thing secret. Maybe the Gods have taken notice and rain down their divine wrath of the potential threat this PC could pose if allowed to continue. Personally I find the prevention is easier and better.

Your player is trying to "Win the Game!" which is a super bad sign. D&D isn't really an "I Win" type of game. You adventure until you feel the characters deserve to rest or you wish to change character or setting, and so on. There can be a narrative end but no real overall victory or defeat on a whole game level. That's the point of D&D. It's not a videogame. Players who seek to find all the exploits for an 'I Win D&D' mentality just break the game into unfun chores.

This is also why games like these have Gamemasters - be it "Dungeon Master" or "Storyteller" or such. This role is so there is somebody to change what must be changed, adapt to the group, and provide the world the players will play in. This means you, not the books, decide what the rules are.

If the player refuses to play by your rules - remove them. You don't need that toxicity in your games.

ty for your input. ill take it into consideration. also they would use there 9th level slot to cast wish to cast simulacrum. no item cost.

Quote from Geann >>

Rules as Written.  "If you cast this spell again, any duplicate you created with this spell is instantly destroyed."  So you can only have one Simulacrum at a time.  You can use Wish to duplicate the spell Simulacrum, but that does not allow a second Simulacrum, it just replaces the existing one.  You could use Wish to create a similar copy without destroying the original, but that puts you in the land of Stress and a 33% chance to never be able to cast Wish again each time you do it.

The Simulacrum has half the hit points of the caster.  If you have your Simulacrum cast the spell, the new copy has half the hit points of the copy.  You're not going to ride roughshod over much of anything with a bunch of sims that have a quarter or less of the hit points of the original caster.  A simple AoE spell is going to wipe out most of the herd.

 IF the Simulacrum creates a copy of the original caster then its half hp of the PC still. so if joe is the caster makes rob, rob now makes cody from joe, cody now makes carter from joe. and so on all the while using wish as its regular spell version meaning no stress involved.

This sort of thing came up before with the infinite simulacrum. I suggested a ruling, which is admittedly splitting hairs, but here it is. The simulacrum has the spells you had when you cast the spell, but since you cast your wish to create it, you finished casting the spell (just) before it was created. Therefore, it does not have wish, and has no way of regaining the spell, so it can't just keep wishing for a new one.

That wouldn't stop the caster from memorizing simulacrum before he cast wish and still doing it, but in that case, he at least needs to have the material components.

There's a larger issue at play here, however, and I think that's the one you really need to address. You're in danger of losing control of the table. You are in charge, not the player, and not the rule books. Explain to the player that what they are proposing may be allowed by RAW, but its still a dick move, and you aren't letting him do it. You can say simulacrum doesn't exist in your world. Or wish, for that matter. Or as others suggested, a god finds his actions annoying and a blue bolt of lightning comes from the sky and kills him, disintegrating the body and scattering the ashes. The remaining characters hear a voice from the sky telling them his soul was destroyed along with his body and that nothing, not even a wish, will be able to bring back the foolish mortal. The the dude can roll a new character or just find a new group.