Question: Can you only have one instance of certain summons?

[Valerius]

Originally Posted by Redeyes

You can also wish for unique beings that already exist, and if you do and someone else already owns it you'll get control of the unit instead. (Items should disappear, as wished for units aren't commanders by default and need to have Gift of Reason thrown on them.)

It will actually bring the wished for unit to the caster's province and you'll have to fight it. I don't think it's used much anymore without gem gens fueling wishes but if the unit had valuable unique magic items you could try setting up a charm squad to get the commander and items or just kill it outright.

Note that this only applies to commanders, which of course they would be if summoned through the normal summoning spells. But if instead of using the normal summoning spells I wish for a unique that has not yet been summoned/wished for they will of course arrive as a troop and needed to be GoRed. If someone else wishes for the unit before it has been GoRed then the second summoner will just receive the unit as a troop and not have to battle it as they they would if it had commander status (and of course even if you had to battle the summoned troop it would just retreat and die without any commanders on the field). Not that anyone would do any of this.

Interesting note: bodyguards will travel with a wished for unique commander so your welcoming party will have to deal with them as well.