What are the pros and cons of Saving and Sacrificing

The choice between saving or sacrificing has 4 distinct effects.

Character:

• Save: will boost your Life level, which increases your DEF and the amount of HP you can heal. It does not increase your HP, only how much you can heal.
• Sacrifice: will boost your Magic level, which increases your ATK.

Depending on the difference between your Life and Magic level, your arm will either be divine (Life level higher than Magic level), neutral (Life and Magic level approximately the same), or dark (Magic level higher than Life level). This may or may not improve the effects of your Sigils.

Inventory:

• Save: gives you a Life Essence (LE)
• Sacrifice: gives you a Soul Essence (SE); not to be confused with Soul Shards.

Combat:

The effect depends on whether you are saving or sacrificing an enemy or ally.

• Save an enemy: recovers some of your HP.
• Sacrifice an enemy: replenishes your offerings.

• Save an ally: drains half of your remaining HP to revive the fallen ally.
• Sacrifice an ally: casts a powerful spell and kills the ally. You will need to use lacrimae (Librom's "not" tears) to undo their death.

Avalon Pacts:

Some quests need to be unlocked by completing a previous one. The choice between saving or sacrificing can determine which quests you unlock. You can always redo the quest and make the other choice to unlock the remaining quests; in other words, no quest is missable.