Tower of Eons

Twelve total mana to gain ten life, split across the four to cast and the eight-plus-a-tap to fire. That is the whole transaction, and it is a worse rate than almost any lifegain effect printed before or since. The card sits in a pocket of colorless artifacts whose casting cost is trivial but whose activated ability is priced to keep it out of decks that mean it: a permanent you can drop cheaply, on the theory that it might pay you back many turns later. The trap is the sequencing. Eight mana plus a tap means the payoff lands long after you have already spent four mana on something that does nothing, and ten life is rarely the answer to whatever was actually killing you. The design reads as colorless filler meant to give artifact decks an option in any color, not as a card built to win games. Where it earns a glance at all is the static fact of being a colorless artifact that produces life, period: any strategy that wants its artifact count high, or that wants a lifegain valve available regardless of its color identity, can run it without bending its mana. That brief is narrow, and the activation cost narrows it further, but the slot is genuine.