While other options like Traxos, Scourge of Kroog and Karn, Silver Golem might tangentially reward artifacts in your 99 (as if you have much of a choice with a colorless deck), Liberator offers an explicit benefit in being an objectively better Shimmer Myr
A three colour, four mana 3/3 that's sometimes a vanilla 6/6 just doesn't cut it no matter how many Steven Tyler-like ribbons it attaches to the spear it's holding
It's not infinite but with a bit of luck -- or with Scute Swarm to make things easier -- we can loop this process a couple times to ramp out a ton of lands and make a ton of creatures
A 36-pack box gives the same pod a larger prize pool
That goes double for its Enchanted Rare variant, which sees Tink go from simply towering over Hooks pirate ship to picking it up in her enormous hand and staring unimpressed at its crew
Then, we can play a fetch land like Escape Tunnel, Evolving Wilds, or [[Terramorphic Expanse] to double Tifa's power twice, making it an at least 20-power trampling attacker that should be able to win the game in one attack, as early as Turn 3