This means it can stopped by Stifle effects but not Counterspells
Its very easy to have a lot of Land entering the battlefield in Green, and that makes this, combined with any potential token nonsense you might be doing, an incredibly powerful card for a very low cost
Any opponent who wants to challenge this character will have to discard their full hand to do so, making it hard to stop her effective lore generation without a Banish card or a major sacrifice
The power level is high enough for it to be here, but still Im skeptical
That said, there are not all that many different archetypes in black green that want mana creatures except the rock (which is arguably about 6 different archetypes depending on the build) and as Birds of Paradise is a better fixer and ramper the Elves of Deep Shadow are only there to offer redundancy to other better cards
This is a personal preference for ratios of certain cards and a well spread mana curve built into a cube however if you are building a cube based more on power level alone it is hard to cut Swords, even this one