Rares are where you start seeing more powerful build-arounds, board wipes, pushed creatures, unusual enchantments, premium lands, and cards with effects that would be miserable if they appeared too often in Limited
Martyrs' Tomb Rarity: Uncommon TYPE: Enchantment SUBTYPE: - CMC: 4 Mana cost: USD: $0.17 EUR: 0.14 TIX: 0.06 EDHREC RANK: 27709 Pay 2 life: Prevent the next 1 damage that would be dealt to target creature this turn
(8/25/2015) Face-down cards in exile are grouped using two criteria: what caused them to be exiled face down and when they were exiled face down
They do come with a cost to sacrifice, but are still worthy
theres also something to be said for its greatest use requiring you to have a handful of lands but this sees a fair amount of play and is incredible with landfall commanders like Tatyova, Benthic Druid and Tannuk, Memorial Ensign that keep cards flowing