Urza's Saga and Nettlecyst are established cards in Legacy.
Michiko's Reign of Truth is not and yet ... this card seems just as powerful ... given the right build.

Consider this opening :

T1 Ancient Den, Esper Sentinel
T2 Urza's Saga, Michiko's Reign of Truth and that is a 4/4 Sentinel attacking on T2.
With another Artifact Land instead of Saga on T2 and possibly a Mox Opal and/or Mishra's Bauble in play this can be even a 5/5 or 6/6 ... attacking on T2 and T3.

Other potential T1 Artifact Creatures to consider :
Hope of Ghirapur has Flying to help connect and can possibly stunt the opponent's development. Losing the artifact in the process is a minus though.
Haywire Mite is a very intriguing option because this creature can still use its sacrifice ability while being tapped / attacking. Needs green mana though.
Ornithopter best of the 0-mana options because of the flying ability but less useful without Michiko's Reign of Truth. Can pick up a Nettlecyst and become a very dangerous flying threat.

Add in the rest of the usual suspects in an artifact build and this could be a tough one to deal with ?

//CC0
4 Mox Opal
4 Mishra's Bauble
1 Ornithopter

//CC1
4 Swords to Plowshares
4 Esper Sentinel
3 Hope of Ghirapur
3 Haywire Mite
2 Enlightened Tutor
1 Shadowspear
1 Gingerbrute

//CC2
4 Patchwork Automaton
4 Michiko's Reign of Truth // Portrait of Michiko
2 Ethersworn Canonist

//CC3
4 Nettlecyst

//Lands
4 Windswept Heath
4 Urza's Saga
4 Plains
4 Ancient Den
2 Tree of Tales
1 Savannah