This is extremely powerful, especially in EDH. Repeatable tutors tend not to be this cheap. Also, it's very odd to see green being a part of tutoring for artifacts.

If you look at the limited archetypes for the set, I'm doing GU Artifacts and UR Auras.

Having trouble thinking of an evergreen keyword to put on this one, but I want to make the cycle consistent. Any ideas?

It's hard for us to answer that without seeing the rest of the cycle. Who else is in this cycle?

All 10 of the bicolored three-drop uncommons who enable their limited archetypes. The enemy colored ones each have a keyword ability and an activated ability, and the ally-colored ones each have a keyword ability and an triggered ability with an optional cost.

...I meant specific card links. If you're wanting people to help, it's good to give them all the info they need in order to help, not require them to go digging through your card file. I assume from context that Trianna's Enchantress is one. Who are the other eight?

• Eccentric Tinkerer
• Trianna's Enchantress
• Pontiff of Helgrind
• Deepcavern Miner
• Sunsword General
• Infantry Tactician
• Preacher of Ellesméra
• Lieutenant of Tronjheim
• Bloodstalker
• Market Bandit

­ is a tough cookie pair, since they don't share any evergreen keyword. I note that about half of your purger cards from this cycle use an unshared keyword, so why not do that? Flying isn't used yet, and neither is hexproof. Aiming to use each keyword one would be a challenge though. I think you've used Flash and First Strike twice. (I'm writing from my phone and it's a bit harder to look them all over.)
In the Cards With No Home set I proposed "faze" as an evergreen keyword. You could use that, if you're interested.

I would like to point out that this of a powerful combination of abilities. You'll find that not many cases do repeatable tutoring these days, and that none also have hexproof. I feel this would be write popular in the right EDH decks.

I have my keyword.