I only have that one copy. Still, it looks like I'd need 3 more copies of Phoenix to surpass base Hecatoncheires in attack. That's a lot of time/resources needed to squeeze out a marginal advantage*, when I still have more farming to do on the Apocalypse side.

*I switch up elements according to the event. Makes progression significantly slower, yes, but the rotating keeps the game fresh for me. Whatever gain I'd get from a max Phoenix over base Hecatoncheires would only be exercised in dark events. That pushes the expected effort/reward ratio low enough that I'm doubting that it's worth it for me. It might be acceptable for me to gamble on my friends list sticking with Phoenix for light.

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As for your space issue, have you considered throwing a few hundred jewels at inventory expansions? A few tens of slots buys you some breathing room for the time being. Then later you hit the point where you can occasionally burn some enhance materials on mismatched elements to create room to accept incoming new stuff, while still retaining a reserve for future usage.

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Whoops, got the effort/reward ratio flipped around. It should be high effort/low reward.