BONFIRE ASCETIC
A bonfire ascetic allows you to revive the area boss and all enemies that might have despawned, but it raises the difficulty to the next new game. This allows you, for example, to obtain duplicates of a boss soul without having to play through the whole game again.

DS1
In DS1 the only way to repeat a boss fight was to finish the game and start a New Game cycle. To get all the boss weapons for a certain boss would require multiple play-throughs, a time commitment that not everyone can afford.
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SOUL VESSEL
A Souls Vessel allows you to re-assign levels points across the character abilities, thus avoiding the need for creating new characters to experiment with different builds.

DS1
Once you had committed your hardly earned souls to increase this or that character’s ability, that was it – in order to try a different build your only option was to start over with a new character.
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RING OF NAMES
A great way to make online match-making with a friend easy, perfectly integrated in the game world and lore.

DS1
Trying to co-op with a friend in DS1 was a random business, sometimes it worked right away, some other times you had to wait for ages and/or quit the game and restart it in order to be on the same server. Not to mention the possibility to be summoned by someone else in the meantime. A true pain in the neck.

DS3
Password system. More efficient, but immersion-breaking.
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SMALL SUMMON SIGN
This item single-handedly increases DS2 re-playability enormously by allowing co-op after the area boss has been defeated. You can set up mini-missions assisted by a friendly summon, to explore the area better, or collect loot that you’ve left behind in your first run of the area.

DS1
In DS1, once you defeated the boss, you could no longer engage in jolly cooperation in that area in your world. Until, of course, your next New Game.
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TOKEN OF FIDELITY
Using this item as a phantom will restore the master’s health, no matter how distant the master is from the phantom.
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COVENANT OF THE CHAMPIONS
An excellent, built in way, to raise the game’s difficulty level. As with the Ring of Names the designers have found an elegant way to integrate a difficulty-level setting into the game world, making it a covenant you can join and leave at any time. Added bonus, upon joining the covenant you receive a tablet that you can examine to check a leaderboard of the best ‘champions’ of the game.

DS1
There simply was no difficulty-level setting in DS1.
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COFFIN OF SEX CHANGE
In the Things Betwixt area a mysterious coffin can be found on the sandy shore of a subterranean lake, guarder by two big stinky ogres. Once you enter the coffin, your character will lay in it and after a few seconds he/she will come out of the coffin as a member of the opposite sex.

DS1
There was no way in DS1 to change your character’s sex once you committed to it during character creation.
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SOUL MEMORY
I know this is going to be very controversial, but I think Soul Memory (SM), although far from being a perfect way to measure a characters ‘powers’, is a better way to use than Soul Level.
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END OF GAME BOSS
Not forcing the player to restart the game after the final boss has been defeated.
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DE-SPAWNING ENEMIES