Mob casting non-combat spells in combat

Maglivale's obviously in combat with me, but seems to be able to cast invis, etc. (531hp 104m 718mv 6368tnl (54.77%) wilderness) You parry Maglivale's pierce. You parry Alisindara's punch. Alisindara's punch nearly strikes you before you turn it away. Alisindara parries your stab. Alisindara dodges your stab. Alisindara is covered with bleeding wounds. (531hp 104m 718mv 6368tnl (54.77%) wilderness) drop 1. Maglivale utters the words, 'uizug'. Maglivale fades out of existence. Maglivale fades into existence. You parry Maglivale's pierce. You parry Maglivale's pierce. You parry Alisindara's punch. Your stab devastates Alisindara! Your slash decimates Alisindara! Your stab decimates Alisindara! Your slash mauls Alisindara. Alisindara is covered with bleeding wounds.