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.Eldrazi Temple can provide two mana from one land, but only for a particular job. Its stronger ability produces two colorless mana to cast colorless Eldrazi spells or activate abilities of colorless Eldrazi. For other purposes, it can still tap for one unrestricted colorless mana.
That makes it a valuable accelerator in decks built around creatures such as Thought-Knot Seer, Reality Smasher, or larger colorless Eldrazi. The mana can pay actual colorless symbols as well as generic requirements when the spending restriction is satisfied. A turn in which Temple helps cast an Eldrazi can be meaningfully faster than the same sequence using ordinary lands.
Read the restriction carefully when planning other plays. The two-mana ability cannot pay for an arbitrary artifact, even if that artifact is colorless. It also does not qualify merely because a spell has an Eldrazi-related name. The spell needs to be both colorless and an Eldrazi. Devoid can make some spells colorless, but you still need appropriate sources for any colored symbols in their costs. Temple is strongest when many of your important plays qualify, rather than when the deck contains only one enormous Eldrazi finisher. Its ordinary colorless mode keeps it functional between those plays, but a multicolor list may still feel the missing colored source. Build the mana base around the actual mix of spells, and count Temple's second mana only in the turns where its restriction allows you to spend it.
