Had an idea similar to the one Shindori posted back on page 2. To summarize/recap: you can relive ancestral memories that let you experience the battle between the Lords and the Everlasting Dragons, with your covenant determining which of the great lords you fight alongside. Thought it was a very interesting one which deserved some expansion!
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My area would pretty much be the same (various different areas of the battlegrounds between the Lords and Dragons) but getting there would be done differently. Doing so would require finding an everlasting dragon, perhaps the same one that grants entry into the Dragon Covenant or possibly even another one if the Ash Lake area could be expanded. Upon reaching the dragon, you would offer a Lord Soul to it. The dragon would take the soul and use its own memories of the battle, combined with the memories within the Lord Soul, to transport you to the battle near the location of the lord in question.
Of course, the Four Kings soul is just a series of fragments from Gwyn's, so presumably those would give brief 'previews' into Gwyn's section, which could otherwise not be accessed until NG+. Seath's soul is also bequeathed from Gwyn, but that would include scenes from Gwyn's battle as well as Seath's fight against his brethren for eye-candy. All in real time, of course. No cutscenes.
Naturally, these areas would be incredibly difficult. You would be combating everlasting dragons, either in your own gear - as if you'd been dropped into the past entirely - or decked out in Silver Knight equips, Gravelord items, etc. depending on which scene you're in. Each enemy would have to fight as aggressively as Kalameet, albeit with less health and damage in order to make these scenes even
possible. Presumably they'd look just like the dragon we find in Ash Lake, but mobile and killable. Gwyn's preview scenes would be easiest, followed by Nito's (you'd be given immunity to his AoE miasma), then the Witch of Izalith's (gotta dodge that fire), and finally Gwyn's true scene as the hardest one and the only one unavailable until NG+.
What kinds of bosses would you expect for these scenes, considering that the regular enemies are
everlasting dragons? Well, do you recall the size of the dragon skeleton shown in the 12-minute DkSII gameplay vid? The dragons were not all the same size, and I suspect that the oldest, most primeval (if that makes any sense) dragons would eventually approach immense sizes. I propose that the bosses would be dragons so large that they dwarf anything else in the game. Upon slaying these monsters, which could wreck bosses like Kalameet or Manus with ease, the player would be returned to the present and granted a ton of souls. Also the lord soul would be returned to the player, for placement into the Lordvessel.
Alternatively..... Each scene would grant the player a unique item, either some piece of equipment used by one of the lords or the soul of each given scene boss which could be used to create incredibly powerful items (or traded into Snuggly for god knows what).
However! Upon your return, the everlasting dragon that granted you that glimpse into the past dies from the strain. Along with the aforementioned treasure, you get back the Lord Soul you gave it in the first place, and you are unable to access any further scenes in that playthrough. To access the others, you must go on to NG+ and acquire another Lord Soul. However, the scene may or may not be
even harder. So if you started with one of the bequeathed LS scenes in NG, and proceeded to the NG+ Gwyn scene, you're in for a rude awakening. But then again, would you rather wait until NG+5 to do that one? Decisions, decisions!
TL;DR....