Skulls of the Shogun

This achievement is for bringing your total gametime down to under 3 hours; it can be done on casual difficulty, you have as many attempts as you want on a level and you can use the normal playthrough save you used to beat the campaign in the first place. On some levels, you can knock out several of the gold skulls while attempting a speedrun, for example if there's a very fast strategy for killing the general and also a gold skull for not losing any units, but you should generally separate gold skull and speedrun attempts. Try for the speedruns first just in case you do luck into a few skulls.

Worth noting is that time only ticks up when you're actually playing. Enemy turns, cutscenes and so on don't mess with your time, so don't stress about it. Also, you only need to focus on this first half of the game. I had some terrible playtimes towards the end, like 32 minutes on the final stage, and I didn't have to bother with tightening up the times that late in the game. I started from level 1 and tried to do each level as fast as I could, and my achievement popped at the end of "season 3."

For most levels, it just boils down to rushing ahead with your best troops and general as fast as you can. Just push hard without caring if you lose a few soldiers on the way. This generally applies to the first half of the game, and I will only note specific strategies for levels that need them. Level 1, for example, doesn't really require anything you shouldn't already know after beating the campaign; just try to do it faster than you did last time.

Level walkthroughs

These are the levels I had to retry a few times to get the time down, so I wrote down what I did. For every other level, just rush and go for the objective as soon as possible.

04. Glorious Gates
Round 1: Send up a Cavalry on each side to strike the enemy Archers on both sides. Follow up with each Archer on your side to take out the enemy Archers. Run another Cavalry, either side, up as far as you can.
Round 2: The enemies will likely have rushed your Archers with everything have, leaving their General wide open! Rush and attack him with all close-by Cavalry. If an Archer on your side survived, he should be able to move up and take the final blow. If not, rush the last Cavalry up as far as you can and use him to kill the General in round 3.

If the above fell apart in round 2 because they killed your Archers and/or Cavalry, just restart and try it until you have 3 Cavalry and 1 Archer within range of the General.

05. Sakura's Solace
Round 1: Rush your Cavalry along the north path, as far as they can go. Move your Infantry to haunt the rice paddies in front of them. Follow the Cavalry with your General, as far as he can go.
Round 2: Keep rushing the Cavalry even further, follow with the General and move up to the next rice paddies with the Infantry.
Round 3: The enemy should've attacked your General and Infantry, leaving your Cavalry to rush straight at the enemy General. Attack at a up/left diagonal angle to push him off the edge and win.

Retry the level if the enemy attacked and killed your Cavalry between rounds 2 and 3, or if their General moved.

06. Pink Pursuit
Head up towards the right with all your troops, haunting rice paddies and shrines as you go. Kill any enemies, with Archers shooting first and Infantry or your General finishing them off. Keep rushing to the bridge in the north, not bothering to capture the second Fox shrine (unless you get a perfect opening) or recruiting more troops from the shrine. Keep in mind that you can run past the last few enemies as soon as there's an arrow on the bridge.

08. Guardian Gardens
Rush towards the enemy General with all your best soldiers; Archers, Cavalry and your own General. Try to take out his Archers as soon as possible, then use your own Archers to damage any enemies that get close, and use the General to finish them off and eat their skulls. If you rush hard enough, he won't have time to get any rice paddies and won't have any reinforcements. When I played it, his healer Foxes just ran off and tried to capture paddies instead of sticking around and healing, so you might want to retry until that happens for you.

09. Raiden's Rampage
Take your Infantry, Archers and General and bumrush down the middle. The enemy will do basically the same. By round 3, you should've lost both of your archers but have your Infantry and General with the enemy General right in front of you. Hit him with each Infantry and finish him off with the General and you should be able to have this done in less than a minute.

10. Murderous Moats
Start the level off by knocking the other guys off, it's pretty easy, and eating 2 skulls with your General and 1 skull with the Salamander Monk. In the next room, you can go up against the fallen log directly south of the Salamander and summon an Oni on the enemies there. Next turn, summon another Oni on the enemies and keep attacking them yourself as well. After a couple of rounds of that, you should have a demon General, a demon Archer and a demon Salamander, and have only spent about 3 minutes getting them.

Once you move on to the final area, take your General, demon Archer, demon Salamander and two Archers and head down the south path towards the enemy General. Damage any incoming enemies with Archers, finish them off with your General. Eat skulls to upgrade your Archers and keep rushing. When I did it, the enemy General focused his attacks on the north path and went for my remaining guys there, and there was only one or two enemies protecting their General. With four ranged attackers and a demon General, killing theirs becomes pretty easy.

11. Hurricane Plain
Run one Cavalry north to grab the Fox shrine and the paddies up there, run the rest of the southeast towards the enemy General. Bring your General, stop him off to pick up the Salamander on the way. You will meet very little resistance down here, while the majority of the enemy force runs to the north and kills your idling soldiers. Grab any worthwhile paddies and the Fox shrine here. Buy an Archer from the summoning shrine as soon as possible. Make good use of your Archer and Salamander, taking out any enemies that come down to the southeast corner while eating their skulls with the General, Archer and Salamander. Remember to heal with your Fox, pretty much every round. Move all your troops in that area to the bamboo bushes. Once they're all close enough together, rush for the enemy General and attack him with everything that's alive. You should have a few demon soldiers, especially your General, and he shouldn't even awaken in time to stop you. This might take a few tries as it depends on what the enemy does, but it's consistent enough.

12. Forsaken Flights
Just hurry up the stairs on the right with all of your troops, waiting with the faster ones for the slower ones to catch up. About half the enemy force will come to you, the rest won't move until you've entered the plateau area at the top. Enemy behavior here seems to be random; sometimes they rush down the left stairs and grab paddies and shrines, other times they come down the right. You want them to come down the right and fail to get any paddies or shrines anywhere on the map. If they don't, you can just pick them off one by one as they step into range on the right staircase and eventually gather your troops almost at the top of the second set of stairs. Once you have them all there, you should be able to take Archer potshots at troops and finish them off with something else. Let your General eat most or all of the skulls as he'll be pretty badgered.

Reference times

And here are my times for each level when I unlocked the achievement, as a reference for what to go for:

01. Line Limbo - 04:44
02. Bedlam Beach - 05:09
03. Archer Ambush - 04:14
04. Glorious Gates - 01:03
05. Sakura's Solace - 00:39
06. Pink Pursuit - 06:19
07. Potion Panic - 04:26
08. Guardian Gardens - 03:29
09. Raiden's Rampage - 00:52
10. Murderous Moats - 06:00
11. Hurricane Plain - 06:55
12. Forsaken Flights - 07:24
(This is where I stopped grinding to lower my times and the achievement popped, the times listed below are from my first attempt at the levels.)
13. Fujin Falls - 12:25
14. Lion's Labyrinth - 13:17
15. Chaos Canyon - 05:58
16. Autumn Assault - 10:45
17. Glassy Glacier - 07:38
18. Avalanche Alley - 10:24
19. Frozen Finale - 24:42
20. End of the Line - 32:55

Total: 02:49:25

As you can see, it can be brought down to 2 hours and 30 minutes or even lower if you attempt to grind the whole game. This achievement is a lot easier than it sounds.