Cult of the Lamb

NOTE: The description for this achievement is completely wrong. This achievement has nothing to do with the upgrades you unlock with the points you get for giving Sermons. Instead, this achievement unlocks when you unlock all 12 Rituals.

All but one Ritual are unlocked the same way: collect three Commandment Stone fragments to assemble one, then redeem this in the Commandment section of your Temple for either a new trait for your Followers or a new Ritual. Note that, even though you get two choices per Commandment Stone and only get to make the choice once, nothing is missable. You may have 12 different Rituals than other players, but there will always be 12 available and unmissable Rituals to unlock. So for the Commandment Stones, you'll need to use them in each of the five categories (Afterlife, Labor, Obedience, etc.) four times each, to unlock all available Rituals in this section. The only uniquely-unlocked Ritual is the Brainwashing Ritual. This is unlocked from Sozo in Spore Grotto. Refer to Transmute (30G) for information on that.

As for getting the Commandment Stone fragments for the other Rituals, there are three ways you can obtain them:
 

• Level up a Follower's loyalty level
• Defeat a Bishop (rewarded for each re-defeat as well)
• Collected randomly during Crusade runs

The third option is pretty rare, so you shouldn't count on it. The first two will be your main sources of these fragments. You'll get a fragment every time you defeat a Bishop, and since you need to defeat all four without taking damage for four other achievements, you'll assuredly take multiple attempts per boss, and therefore end up with many fragments during your runs of those achievements.

As for the loyalty levels of your Followers, this will be your primary source of fragments. While there are multiple things you can do to increase Followers' loyalty, you'll mainly be increasing by giving Sermons every day and doing side quests for Followers. They will occasionally run over to you and want to talke, giving you a simple quest and around three or four in-game days to get it done. They're always very simple and quick to complete, and give significant loyalty to that Follower. You can also give them gifts and speak to them to increase their loyalty, but honestly that isn't necessary. You'll level up enough Followers just from Sermons and side quests that you don't really need to go out of your way to increase their loyalty. As long as you give a Sermon every day and complete all of the quests your Followers bring to you, you should easily unlock this achievement well before finishing the game, let alone all other achievements.