Skaven - Redmaw Plague

[ionic osprey]

a) if enemy hero have artefact i can use it right ?

b) at start of the combat phase there no unity from my army i can use enemy hero right but what happen if my unit pile near him ? can i still use him ? ( i think yes because condition for that plague is at start of the combat phase )

[peak spindle]

Yes to both.

[ionic osprey]

and if i pile near that hero with plague .. enemy can now activate him and use him right beacause he is stil hes unit and now he is in combat