there's nothing built-in as a full system of what you want, but you can certainly do/create everything you want to do for your game.
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the built-in 'pov' Object Attribute of the 'game' Game Object (game.pov) allows you to change which character (Player Objects: the default new game Player Object is the 'player' Player Object) you're currently controlling. You can only control one character at a time though (no MP mud/mmo type stuff with quest), via the 'ChangePov()' Function (
http://docs.textadventures.co.uk/quest/ ... gepov.html ).
there's also two different locations for your 'look' character descriptions, one location for when you are NOT controlling the Player Object (effectively is like a npc/party member), and another location for when you ARE controlling the Player Object, this always causes confusion in people, in why their 'look' description Verb isn't working.
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this is just a start, feel free to ask questions, we'll be happy to help you get set up whatever you want in your game, if you need help with anything.
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P.S.
see Pixie's Combat Library and Demo game, as it has equipment and spells (if the full range of types of spells can be done, then "abilities" can be done, as what's the difference, lol). Though, this stuff is not easy stuff for new people to quest and/or especially to coding.