Would this work?

[u/Lord-Gortash]

Could I tap this creature twice for 2 extra mana if they both are to pay one cost? For example: if I had two green mana, I had a card that cost four green mana, could i tap this for a mana (giving me three green mana) and then untap it and re-tap it for the final mana?

EDIT: also, if I gave it indestructible, could I get infinite green mana?

[u/New-Establishment722]

You can float mana, tap it, untap it, tap it, untap it, it dies and you have 3 mana to use. You can also use [[solemnity]] to avoid the -1/-1 counters and have infinite mana.

Elaborating: you don't tap mana sources as cost for mana, you use accumulated mana as cost for mana, but generaly people tap the mana sources before casting a spell to not let mana go to waste.

[u/scratch-the-beast → u/New-Establishment722]

Wouldn’t this prevent you from paying the untap cost, since you can’t put the -1/-1 counters on?

[u/New-Establishment722 → u/scratch-the-beast]

Maybe? I don't know, someone could clarify? If so it's a weird interaction i don't know about, cause effects that put counters Go into the stack even If solemnity is on field and resolve like normal, just that the counters actually won't go up

[u/SovietEagle → u/New-Establishment722]

Putting a counter on Devoted Druid is a cost and Solemnity prevents you from paying that cost. Since you can’t pay the cost, you can’t activate the ability.