Completing Code Vein, and getting all achievements for it, is a bit harder than just beating the game once. In fact, it’s not possible to get all achievements in one playthrough, but requires at least three. I’ll give you a few tips to minimize the number of playthroughs you’ll need, and in particular point out a few of the less intuitive pieces of content.
Naturally, there are spoilers ahead.
The first thing you have to keep an eye out for are Vestiges. Vestiges provide new Blood Codes, as well as unlocking certain skills. Most are out in the open, but a number of them are hidden in boxes or other breakable items. As a result, you absolutely have to break everything, like the shattered tube, above.
Completing Code Vein means getting all three endings, which tie-in directly with Vestiges. The endings are based entirely on how many of the Successors you “save,” instead of killing. This is based on recovering all the Vestiges for their respective Successor before you tackle their boss fight. Doing them all nets you four Blood Codes, and the true ending, but you also have to find, and unlock, all the Eos Vestiges with Io to get a bonus ending scene. The true end also gives you another Blood Code.
Going for the best ending means you’ll miss certain Blood Codes though, the ones you get from failing to save the Successors. I didn’t even realize they could die on my first playthrough, but if they do you get a different Code. As a result, to get every Blood Code in two playthroughs you need to reach the bad ending — where you fail to save any Successors — and the true ending, one after the other. This leaves the boring neutral ending for last, which requires you to save at least one Successor, but fail to save them all.
The Cathedral area has another secret Blood Code you’ll need for completing Code Vein. It’s hidden at the source of the blood beads, behind the Successor door guarded by Isis. The Code appears once you’ve defeated the last Successor boss in a playthrough.
Other than the endings, the most important part of completing Code Vein is the Depths. There are some Vestiges to find here, but the main reason the Depths are important is because of your ability to grind Marks of Honor. If you haven’t been playing multiplayer you’ll only have a half-dozen, or less, from the handful that can be found (per playthrough). Every time you defeat a boss with another human both of you are rewarded Marks of Honor. A lot of these Marks are needed to get an achievement, but thankfully in the Depths you get one from every mini-boss fight, and the visiting player isn’t disconnected after the fight like they are after regular bosses. If you go to a Depths map you’ve already cleared, the main boss is also available to fight without having to find the key to their door again.
Visiting all Depths maps also gets you an achievement, but you’ll only find around half the maps by playing the game normally. The others need you to do some quests, and either require a lot of exploration, or a good guide. I suggest the guide, since visiting the right NPCs in the right order is tedious even without having to explore to find them.
Many other achievements are easy to get with normal game play. Unlock Vestiges, pay to unlock Gifts, and use a wide variety of Codes, and you will find yourself with a few more achievements in short order. Completing Code Vein is a lot more reasonable than a lot of other games, despite the hidden unlocks.
