I checked and i don't have that file, which means either you're not playing the 1.05 that was uploaded a while ago or it might be a file from rpgmaker RTP's.
As for the quest, you can do it, it won't have a combat nor any sexual event that ins't avoidable.
Elysion deal light dmg with the soul rhapsody skill, and our heroine has little to no light resistance.
If you beat the secret boss Null and take the item he's guarding, you should have an easier way with him, else just keep Last Sanctuary + Debuff him with -atk/m-atk and you should avoid being one rounded even when he acts twice.
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If you raise your Lust stat too high you'll likely get the "Magical Slut" ending rather than the true one, but i don't know how high.
Corruption will lead to a bad end too if it gets too high, you'll eventually be permanently debuffed with Soul corruption and thus cannot lower corruption past a certain point.
Slime Core comes from Mother Blob, it's the secret boss in Factory Ruins, in a small room close to the endpoint teleport.
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Odd Eggs come from Demon Matrix, he's the secret boss in the Secret Club, hidden in underworld b6f treasure room.
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Dream Key drops from Morpheus, he's the secret boss in the Otherworld Academy, hidden in the pool room.
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Laboratory Midpoint, door on the right, monster pen
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Problem is Soulphonica shares it gather spot with Soul Flower and Blue Rose, i recommend you save before gathering and just reload if you don't get Soulphonica, saves you from sleeping and going back to the same spot if you don't get enough.