­ is not phyrexian mana, but allied mana -- pay with R G or W. I was looking for a more primitive form of creature, and thought "less generic mana", but being all-G would be a bit too much, hence this compromise.

If I get your explanation correctly, what you mean with "allied mana" is what is commonly refered to as tricolored hybrid mana or "trybrid" mana, right?

This is not dissimilar to Marisi's Twinclaws which are cards with one monocolored mana symbol and one hybrid of that color's allies - except that you allow the creature to be cast with an entirely monocolored mana-base.

It should be noted that the mana costs like the one on Marisi's Twinclaws have been identified as harder to understand for players than gold cards or hybrid cards individually.

I don't entirely understand the choice of this approach over e. g. .

I'd not heard tribrid before, but yes.

Well, I'm not sure it works, but my thought is that a lot of the complexity is removed when (a) you can think of a card as a single colour and (b) you don't have to try to read the mana symbol from scratch, you know it's paired with green.