MANAHIVE

“Well of Life” (artifact, colorless) gives life at your end step if you control no untapped lands.

Closest equivalents (same color, similar effect or timing):
1. “Pristine Talisman” — taps for mana, also gains you 1 life (artifact, colorless).
2. “Sunglasses of Urza” — doesn't gain life, but is a similar old-school artifact with a triggered effect.
3. “Tablet of Guilds” — gains life under certain conditions (artifact, colorless).

There is no exact colorless artifact with the same end step & untapped land condition, but “Pristine Talisman” is closest for repeatable colorless artifact life gain.