Senior Member. It needs to be “would attend” if at that time the attendance was in the future/had not yet happened. It's the equivalent of “I was told someone was going to attend”.

Is it attend or attended?

As verbs the difference between attend and attended

is that attend is ("to kindle") or attend can be (archaic|transitive) to listen to (something or someone); to pay attention to; regard; heed while attended is (attend).

Will be attend or will be attended?

I will be attend is wrong sentence.... 'will be' uses in passive voice and 'will' uses in active voice... both senses future tense but in active voice subject "I" is important we r emphasis to person "I" & party is not important. ... ex; Active: I 'will' attend the party. Passive: Party 'will be' attended by me.