I think you should change the costs since it is slightly underpowered. First, you have to waste a zephyr's crest to actually have some use of it. Furthermore, you have to spawn more than 3 creatures to have some next to each other. Maybe you should change it to "Any creature on the field with a creature with Zephyr's Crest gains Zephyr's Crest after 3 turns (2 turns for upgraded)." Maybe this might be OP though, but programming the next to would be fairly difficult I believe since there is nothing yet like that.
what your saying about needing heaps of creatures first to make it more stronger is correct, however about the 'underpowered' part take it from this perspective:
I have a Lava destroyer on the field, I use this on it.
then i summon two more.
As your adding creatures to the field, LD is getting 1/1 per 2 turns/1 turns upg., at the same time your adding 2/2 to the lava destroyer.
lets say with cyclonic crest, in 5 turns constantly adding creatures, lava destroyer would have [1x5] + [2x5] = 5 + 10 = 15/15,
plus your other creatures gain +5/+5 and there would have to be 5 creatures for each to get +5/+5,
so 5+5+5+5+5 + whatever attack they would have had previously. that's a lot of damage though can be countered by rain of fire, killing most of the creatures, and leaving few with the crest and less attack.
with zephyr's crest it would only take slightly more turns.
and don't get me started on mono
decks with this thing
that would be scary
