Cheapest priced copy (Ravnica Allegiance): $0.99 at Card Kingdom, near mint, their price list as of .
Font of Agonies 
Enchantment · Rare · Ravnica Allegiance · #74
Whenever you pay life, put that many blood counters on this enchantment.
{1}{B}, Remove four blood counters from this enchantment: Destroy target creature.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
2 printings · $0.99 to $3.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Ravnica Allegiance Promos | 74s | Rare | — | $2.99 |
| Ravnica Allegiance | 74 | Rare | $0.99 | $3.49 |
2 rulings from Wizards of the Coast
- 25 January 2019The first ability of Font of Agonies is a triggered ability, not an activated ability. It doesn’t allow you to pay life whenever you want; rather, you need some other way of paying life, such as with Blood Crypt’s ability.
- 25 January 2019An effect that causes you to pay life uses the word “pay.” If an effect allows you to choose to lose life or to be dealt damage without using the word “pay,” you’re not paying life.