Adellia, Mercenary for hire

When Adellia, Mercenary for hire enters the battlefield, for each opponent chose a number
from 1 to 10.
Whenever an opponent casts a spell with the
chosen mana value, put a +1/+1 counter on
Adellia, Mercenary for hire.
At the beginning of each opponent's upkeep,
they may pay {1}{p/r}{p/u}. If they do, they gain
control of Adellia, Mercenary for hire until the
end of their turn. Adellia, Mercenary for hire
becomes goaded.