Why is this a blue creature that gains vigilance? Mono-blue has not gotten vigilance since Planar Chaos.
EDIT: Unless the extent of your throwback includes non-modern design choices and use of the outdated color pie, in which case I apologize.

it's symmetric card to Elephant Guard. more elegant, easier to grant vigilance than to untap either using longwinded wording or falling to unintuitive timing.

Unfortunately, vigilance isn't a blue ability and shouldn't appear on the card. It's also more likely to fall prey to bad timing, far more than untapping.

there's plenty of cards that gain vigilance at common. but here it's losing one ability and gaining another. so it's just simpler to use another keyword.

the fact that Planar chaos even made blue vigilance means it is potentially a blue ability. and this card warrants such potential to be realized.

furthermore, they said letting green have vigilance would make it more more interesting. but so far that has been far from the reality. vigilance+reach is no different than vigilance+flying. auras and landfalls and stuff? color me not impressed.

otoh, blue's tight bond with white in regards to vigilance and tapping/untapping allows more freedom and combinations in this area.

that said, i thought of using white mana to activate, and it could be a cool cycle going counterclockwise.

made leader for homebound