I know when a +atk -def +4 is merged to an unmerged +spd -def the result will be that it will be a +5 +spd -def.
But If a +10 is merged to an unmerged would it be able to merge an it will stay +10 or It can't be merged because +10 make it impossible to merge(it's because i want to change the IVS of any possible units that I have in the future that are +10)
Merging a 5*+10 onto a 5* unmerged unit will make the previously unmerged unit into a 5*+10. This is how you change the IVs of a +10 unit.
For example, let's say I have a -Atk/+Def 5*+10 Cordelia. If I merge her onto a 5*+0 +Spd/-HP one, the result will be a 5*+10 Cordelia with +Spd/-HP.
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