How much are enchantments a theme of the set?

I think it's hard to answer in isolation because in a normal set these probably aren't worth it unless you want to splash for a particular enchantment. But in an enchantment heavy set they could make the difference between some decks being playable and not, so it depends which enchantment-based decks you WANT to be playable.

In response to your question, I think this land is wanted in 2 different decks.

1) RGx Minor Gods 2) BR Curses

This land is fantastic in the minor gods deck, as it wants to splash other colors but will probably have trouble doing so. It's fine in the curse deck, but won't be picked as highly as it will in the minor gods deck.

This looks fine to me, and I definitely support allowing for splashing!

A few formatting issues you might not be aware of; This should add not . They changed the rules for coloress mana in Oath of the Gatewatch (I'm not good at explaining it unfortunately, so if you're curious about what was changed, maybe try the MTG gamepedia?)

Secondly, and I'm not sure about this one, but I think it might be better to say "cast" instead of "play", since from my knowledge, only lands are played, while other spells are cast.

And third, magicmultiverse lacks a perfect formatting system, so it can be tempting to include line breaks, where normal magic cards would have them. I recommend against it, generally.

It's probably okay to have a line break on this card, but if you have made a card or ever end up making a card with three or more lines of rules text, white space between each paragraph will make the card less readable than a yugioh card (especially on low-resolution screens).

The third is a purely stylistic choice, though, and you're free to include line breaks if you want to. It looks fine here, to me, but it can be a bad habit. (also notice that full line breaks are much larger on this site than the actual spacing WOTC uses to separate abilities on cards)

@Froggychum: Just implemented all of your suggestions. Thanks! I knew about the Gatewatch change, but for some reason didn't see the option for colorless mana on this site! I'm going to go back to all the other cards that produce colorless in this set and change them.