What happens when you cast Wish while mounted on a Found Steed?

Question

The spells Find Steed (PHB, p. 240) and Find Greater Steed (XGtE, p. 156) both state:

While mounted on your steed, you can make any spell you cast that targets only you also target your steed.

The Wish spell (PHB, p. 288-289) has a range of Self.

What happens when someone mounted on his Found (Greater) Steed casts Wish?

1. Only the caster will benefit from it, since Wish has the potential to affect more than just you (especially if you use it to replicate an existing spell)
2. Both the caster and the steed will benefit from it, but it will have to be the same Wish effect (ex: both doing the 25 000 gp value object appearance)
3. Both the caster and the steed will benefit from it, and will both be able to choose their own effect (ex: the caster replicating spell X and the steed replicating spell Y). Sub-case here is whether the "targets only you" restriction must also apply to the chosen spell(s) or not.
4. Other behaviour

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One crazy scenario I can think of if #3 is true: sitting on a Steed and casting Wish. The Wish you choose is a Simulacrum of you. The Wish the steed chooses is also a Simulacrum of you. You now have a simulacrum controlled by you, and a simulacrum controlled by your steed controlled by you. Absolute bollocks.

Another crazy one: The Wish you choose is [something unimportant]. The Wish your steed chooses is Find (Greater) Steed, so that your steed... controls a steed... And then, repeat it the next day, while the first steed is reduced to mount the second steed (and you are still small enough to mount the first steed), so that you cast Wish for [something unimportant], so that your steed gets Wish to cast [something unimportant], and your steed's steed gets Wish to cast Find (Greater) Steed... Creating a Command chain of Caster -> Steed -> Steed -> Steed. Absolute bollocks!

Answer 1

Option 2: both the caster and the steed will benefit, provided you Wish for something that only targets yourself.

Wish can create many different effects, but choosing which effect you want is part of the casting of the spell, so the steed won't be able to choose for itself the effect it wants. Whatever effect the caster creates will also apply to the steed.

However, the effect needs to be one that "targets only you". Here are the possibilities:

• Duplicate the effects of any other spell 8th level or lower: affects the steed if the spell you are duplicating only affects you (depends on the spell).
• Create one object worth 25000gp: doesn't target you, so it doesn't target the steed.
• Restore all hitpoints to up to 20 creatures: If you only choose yourself, then it targets the steed as well, but you could just choose yourself AND the steed AND others.
• Grant resistance to a damage type to up to 10 creatures: same as above.
• Grant immunity to a specific effect for 8 hours to up to 10 creatures: same as above.
• Undo a single recent event: doesn't target you, so it doesn't target the steed.
• Other (any creative use of the spell): if it only targets/affects you, then it will affect the steed as well (But you could also word it so that it affects the 2 of your regardless).

As we can see, there aren't a lot of actual benefits to sharing Wish with your steed, but you could do some fun things by duplicating spells.