On my opponents turn I pay 1 mask to activate the global on Kitty Pryde- Shadowcat. "Target character cannot attack this turn unless its owner pays 1 life." Next I pay 1 mask to activate the global on Mr. Fantastic- Brilliant Scientist on the same target character. "Target character must attack this turn." Is my opponent forced to pay 1 life and attack? I know that cannot should trump can, but the card reads must. Can my opponent be forced to pay a cost?
If not, if I were to use a global to force an opposing target character to attack, could my opponent then choose to use the Kitty Pride global to avoid attacking since they cannot be "forced" to pay that cost?
Thanks!