I'm not 100% sure how a design doc goes, but this is in no way intended to be a legitimate one. This is just an idea for a video game that I think would be cool. You can tell me if you think it's awesome or garbage or anything in between. The following idea is based on persona, pokemon, demon's souls, metroid, pandora's tower, and other influences. It's an MMORPG with real time action as opposed to clicking on an enemy and hitting numbers (as reductive as that sounds).

The Combat:

You have 4 slots to equip your weapons. If you use a controller, then the d-pad will be used for weapon swapping. There's a large range of different types of weapons, such as longswords, katanas, scythes, maces, clubs, hammers, ninja stuff, etc. All weapons have a spirit/persona attached to them (unique to that weapon). Each persona levels up with use of the weapon/persona. As you level up, you gain more spells/attacks. Physical attacks are combos that you learn to perform, while magical attacks and effects will be performed by the persona. You can choose 8 spells to equip from your equipped persona. So if you divide the spells up as 4, 2, 1, and 1 among the persona, then when you switch to the first weapon, you'll have 4 spells at your disposal.

With regards to how you use your weapons, this is where the demon's souls influence comes in. You can equip a shield in one hand and use a weapon in the other, or you choose to wield the weapon two-handed and get more damage out of it.

Another key part of combat is the chain gauntlet (pandora's tower influence). You start of with a beginner level gauntlet, but as you go on you can collect some with better str/def/etc stats, along with better reach / better luck. In combat, you can use the chain to attach up to 3 enemies together (enemies that you can attach depends on gauntlet's stats). This can keep them grouped and make them easier to deal with. Another use for them is the ability to partner up with someone and attach your chains together. That way, you can cause a large group of enemies to stumble and get sunned and proceed to beat the shit out of them with weapons that have a large reach. This also encourages group-play. Once an enemy has been defeated, you can shoot your chain at it, and go through the pokemon-like battle for its soul/spirit/persona (this is where the chain's luck status comes in handy).

Once / if you capture the persona, you can either A) Collect the materials required to build the weapon that will act as the spirit's vessel (metals, crystals, wood, leather, etc), B) Fuse it with another spirit and proceed with part A, or C) sell it to a vendor who will convert it into mana. Your ability to use certain persona depends on your current level. If you happen to capture high level persona and fuse them to make something awesome, due to being in a large group, you'll still have to level up before you'll be able to use it.

The Traversal:

So you have your feet. You can either walk or run. Once you've reach a high enough level, you can use a persona that has the ability to act as a ground mount and you can move up from a medium speed to high speed mount from there. Afterwards comes the flying mount, as we all know. It follows the same procedure, medium to high speed.

The chain can be used to swing around and for some vertical movement. This is where the reach stat comes in. If you don't have a far enough reach, then the path is blocked for you (vis-a-vis metroid). There are also boots that act in the same fashion (kind of like the ratchet and clank magnetic boots). They enable you to walk on certain surfaces, letting you arrive at previously unreachable destinations (something like walking up a mountain side and into a cave leading to ???).

The 4 Cities of Chaos:

This is just a fun bonus challenge that happens monthly. There are 4 cities across the land that hold a monthly tournament to determine who their next King or Queen will be. The first 120 people that join and meet the level requirement will participate in the tournament. Here's how it will go

Stage 1) 60 man free for all. Just a fun to watch clusterfuck. Last man standing wins.

Stage 2) The next 60 go through the same thing.

Stage 3) 1 vs 1. You know the deal.

Stage 4) If the previous winner is online, he or she can defend the title. They will be automatically teleported to the tournament no matter where they are in the world (so get ready). If they're offline then they forfeit the title (boo-hoo).

The rewards - 1) For that month, you get to have a healthy daily allowance taken from the royal treasury. 2) You get to choose two companions from the royal guard (the members of the royal guard have different stats and specialties). Thus you become a big asset to any group and it makes killing things easier. 4) You get a crown. It's superficial.

Note: If your complaint is "That can't be done with today's tech!", I don't care. This is an imaginary game.