Dynasty Warriors: Strikeforce

You have to collect 20 treasures to unlock this achievement. It should be noted that one of the treasures requires online versus play, which may not be immediately apparent.

For all treasures, you can get them in any difficulty. But in easy difficulty, you'll have lesser XP and material drops, so I don't recommend to play in easy unless you couldn't clear a certain quest on normal or higher difficulty.

Conditions for getting each treasure are shown below. For most of the treasures, you have to complete a quest to get the treasure.

For some of the treasures, I've quoted the exact number of actions required from the following site.
http://multiraid.wikiwiki.jp/?FrontPage (in Japanese)
These numbers are shown in parentheses.


[1] Grand Histories
Chapter 3 completed.

Complete chapter 3 in any story. Equivalent to this achievement.


[2] Meng De's Manual
Game completed as Wei.

Completed chapter 5 in Wei's story. Equivalent to this achievement.


[3] Art of War
Game completed as Wu.

Complete chapter 5 in Wu's story. Equivalent to this achievement.


[4] 24 War Manuals
Game completed as Shu.

Complete chapter 5 in Shu's story. Equivalent to this achievement.


[5] Book of Illusions
Chapter 6 completed.

Complete chapter 6 in any story. Equivalent to this achievement.


[6] Imperial Seal
Victory in many battles. ( = Complete 100 quests)

You can repeat a same quest, but this game has far more than 100 quests (272 in total), so no need to grind for this treasure.


[7] Dragon Ring
Many bonus objectives achieved. (100 bonus objectives)

Again, you can repeat, but perhaps no need to do that.


[8] Shadow Runner
Victory in many Legend quests.

Complete 10 different Legend quests. You cannot repeat the same quest for this treasure.


[9] Awards of Valor
Collected great number of spoils.

You have to store 100 or more items/materials in your storehouse to get this treasure. And also, you need to complete a quest. The number of items/materials in your storehouse can be viewed by selecting "view" at the storehouse menu.


[10] Way of Peace
Won battles as all Musou officers ( = Complete a quest with every playable characters).

There are a total of 42 playable characters and you have to complete at least one quest with each character. Allied officers do not count. Only characters you played to complete a quest count for this. There's no in-game stats where you can view which character has completed any quest, so it's strongly recommended to make a note about that.

ZeroThreshold has pointed out that allied officers do count for this treasure (see his comment for the details). I couldn't personally confirm this, but think it worth a try to do in that way.

Diao Chan and Dong Zhuo will become available as player characters by finishing "Hu Lao Gate" and "Battle of Mei Castle" of "high difficulty" quest (any story).
(Thanks to Kennansoft for pointing this out.)


[11] He's Jade
Fully leveled up a Musou officer ( = Attained level 50 with a character).

Equivalent to this achievement.


[12] Red Hare
Defeated Lu Bu many times. (10 times)

Again, no need to grind. Before you finish chapter 6 for all 3 kingdoms, you must face him way more than 10 times.


[13] War God Statue
Defeated all Musou officers ( = Defeated all playable characters as enemies).

You have to defeat all 42 playable characters in quests. There's no in-game stats to show the progress of this, but you'll certainly get this in the course of completing all the quests.


[14] Banana Leaf Fan
Obtained 1 top-rank weapon.

To get this treasure, you have to make one of the top-rank weapons(the 10,000G weapons), equip the weapon to the character related to the weapon and complete a quest with that character.

To make a top-rank weapon for some character, you need a special material. That material is only awarded when you clear that character's Legend quest.

For example, Cao Cao's top-rank weapon "Sword of Dread" needs a special material named "Wei helmet". This material can only obtained by completing Cao Cao's Legend quest "Duel! Cao Cao" (or by someone giving you this in online trade). This sword can be wielded by any character with a sword expertise of 800 or more, but you must equip this to Cao Cao and complete a quest to get this treasure.


[15] Mo Xie Sword
Learned all top-rank Chi skills.

Make all of the 5,000G chi skills and complete a quest to get this treasure.


[16] 5 Colored Stones
Collected all top-rank Orbs.

Make all of the 5,000G orbs and complete a quest to get this treasure.


[17]Shan Hai Jing
Collected all Musou officer cards ( = Collected all officer cards for playable characters).

You have to collect 42 officer cards for playable characters and complete a quest to get this treasure. Speaking about this treasure, there's no need to collect cards for mob officers. Still, you have to collect the mob cards either way if you want to unlock the following achievement.


[18] Bronze Pheasant
Fully leveled up city.

Basically equivalent to this achievement. See the guides for details.
You have to make all 6 facilities to level 5, and rack up facilities' XP to maximum at level 5. After that, complete a quest to earn this treasure.


[19] 4 Gods Statues
Many multi-player friends.

To get this treasure, you first must have 10 players on your profile list. Then you also have to complete an online quest with one of the players in the list.
(Thanks to GLAZEN 201 for confirming this.)

To add players on your profile list, open City Menu, and select Page 2 -> Profile -> Member Profiles. Press Y button to add players on your list. Your current list can be viewed at Page 2 -> Profile -> Profile List.


[20] Hex Mark
Victory in many VS battles. ( = Won online versus matches for 10 times).

Boosting is recommended here. Versus matches use same online lobby as the co-op play, so you have to convince the other players to play versus games where most players are seeking co-op play. Not an easy task.

Don't forget to set "Private" to ON when you create an online city for boosting.