I have a question about the definition of “Taps for mana”. Does it have to be in a mana ability and does it has to be its own mana ability and does it has to be the mana ability which my Tap is part or full activation cost?
Have following 2 scenarios:

1. I control 3 Mutavault, Urborg, Tomb of Yawgmoth, Heritage Druid, and Mirari's Wake. If I activate all Mutavaults and tap them for activating Heritage Druid's mana ability, do I get GGG or BBBGGG because of Mirari's Wake's trigger?

2. I control a Mirari's Wake and a Havengul Lich and have a Deathrite Shaman in my graveyard. My opponent cast Cytoshape targetting my lich and his activated Mutavault. In response, I activate lich's ability targetting my shaman. After everything resolves I cast the Shaman from my graveyard and my copied Mutavault has Shaman's ability now. If I activate shaman's first ability for mana, will Mirari's wake trigger and I get an extra mana of any color?

Another question regarding a new card from Dominaria, the Damping Sphere.
Will it have any impact on a Forest but enchanted with Utopia Sprawl? What if a Forest with Mana Reflection, do I get to choose?

Thanks
Miao

Damping Sphere
2
Artifact
If a land is tapped for two or more mana, it produces C instead of any other type and amount.
Each spell a player casts costs 1 more to cast for each other spell that player has cast this turn.

Hi,

Thanks for your question. The comp rules have a definition for that:

106.11. To “tap a permanent for mana” is to activate a mana ability of that permanent that includes the {T} symbol in its activation cost. See rule 605, “Mana Abilities.”

1. You're not tapping a land for mana. Not only does the Druid's ability not use the tap symbol, you're activate the ability of the Druid, not an ability of a land you control. The Wake will not trigger, so you just end up with three green mana.

2. No. Deathrite Shaman does not have a mana ability, so it does not fit into the description in the above rule. The Wake will not trigger.

And, Dominaria. So we're kind of in a weird position here, where we technically have some cards (and the release notes), but not the full rules for the upcoming set. While usually we wait for the Release Notes to start answer questions, we don't know the full rules that might be changing here with the new cards, so we're going to hold off on answering Dominaria questions until the release of the Update Bulletin, which will happen before the official release of the set.

Nathan Long
Magic Rules NetRep

Now that we have the update bulletin (and are sure no rules are changing), we can answer this last question:

Another question regarding a new card from Dominaria, the Damping Sphere.
Will it have any impact on a Forest but enchanted with Utopia Sprawl? What if a Forest with Mana Reflection, do I get to choose?

With the Sprawl, you're not getting the extra mana from the land, you're getting it from the Sprawl's triggered mana ability, so the Sphere won't apply. With the Reflection, the Reflection isn't producing the mana, the extra mana is being generated by the land (since the Reflection has a replacement effect). Tapping a Forest for mana means that (because of the Reflection) it's tapping for two green mana, and since it's producing two or more mana, the Sphere will apply and you'll get one colorless mana instead of two green mana.

Thanks,
Nathan Long
Magic Rules NetRep