This seemed like an obvious cycle for our set, since it seems to be popping up automatically in every large set. Unlike other sets, though, I would assume we would want 5 signets that encourage monocolor, instead of smoothing mana bases. May I suggest either one of the following texts?:

­, : Add to your mana pool.

or,

­, : Add to your mana poool.

I like that second one, but it may be harshing a bit too much on red fast mana. , : is probably too weak, though, , : is probably too strong, and , : is probably too situational.

I like the first one. We will need mana base smoothing though, as it is also a multicolored set. Maybe, if the monocolored group ARE the invaders, maybe these are artifacts they brought, and a cycle of lands could be from the plane that the multicoloreds are from.

A cycle of lands affiliated with one half and signets affiliated with the other half sounds sensible.

I agree with Alex, having the signets affiliated with one half & lands the other is a good idea.
I agree with Rourke that, if the aliens end up monocolor then the first idea above is the way to go as an activation cost is fantastically flavoured if we go that way - they either enhance their own mana or convert the lesser/tainted mana of the other colours into their own 'Pure' mana.

These got designed as Idyllic Crest, Sea Crest, Gorgon's Crest, Arctic Crest and Fungal Crest.