Sacred Foundry

Type: Land — Mountain Plains
Set: Zendikar Expeditions #14 (mythic)

({T}: Add {R} or {W}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Sacred Foundry has 22 printings, first in Ravnica: City of Guilds (2005). EDHREC ranks it #73 among Commander cards. It appears most in Edgar Markov decks (23,006 on EDHREC). 1 public deck on TCG runs it. It has 2 official rulings.

Legality

commander: legal
legacy: legal
vintage: legal
pauper: not legal
modern: legal
pioneer: legal
standard: legal
brawl: legal

Public decks that run Sacred Foundry

Break the Chains, led by Caesar, Legion's Emperor

Commanders that run Sacred Foundry most

Deck counts from EDHREC.

Edgar Markov: 23,006 decks
Kaalia of the Vast: 20,875 decks
The Ur-Dragon: 18,750 decks
Toph, the First Metalbender: 15,072 decks
Pantlaza, Sun-Favored: 14,732 decks
Baylen, the Haymaker: 14,654 decks
Isshin, Two Heavens as One: 14,588 decks
Cloud, Ex-SOLDIER: 13,116 decks

Often played with Sacred Foundry

Cards that show up in the same decks on EDHREC.

Rulings

2018-10-05: Unlike most dual lands, this land has two basic land types. It's not basic, so cards such as District Guide can't find it, but it does have the appropriate land types for effects such as that of Drowned Catacomb (from the Ixalan set).
2018-10-05: If an effect puts this land onto the battlefield tapped, you may pay 2 life, but it still enters tapped.