An Entity is a creature. An Enemy is an opponent, and an Enemy Eldrazi is an Eldrazi controlled by an opponent, even if you own it.

It's a pity there isn't a rarity beginning with 'E'.

Silver bordered can invent its own rarity! Although it would probably just look different and have the same frequency as one of the other rarities in the set for printing reasons. Also the rarities usually have a colour not a letter. You could have "un set symbol coloured emerald", but could be made clear (a.) that's emerald not green (b.) if emarald is more or less rare than gold :)

They already did invent their own "Doesn't even appear on the spoiler sheet" rarity :)

I reckon we could call that "Execeptional" and yes, the colour should certainly be emerald.

'Exceptional' Emerald - enticing...