Current questions and answers regarding the map editor.

Ah, it’s easier to do it with a region. You create it right next to the garrison. Then you write a script like this:

EnableHeroAI('Duncan',false);
function garrison(hero)
if hero=='Giovanni' then
SetObjectOwner('Duncan',PLAYER_1);
end;
Trigger(REGION_ENTER_AND_STOP_TRIGGER, 'reg', nil);
end;
Trigger(REGION_ENTER_AND_STOP_TRIGGER, 'reg', 'garrison', nil);

Here, Giovanni is the script name of your hero, and Duncan is the hero who should join. I recommend naming the region 'reg' so you don't get confused later. The script has been tested and works (see screenshots).