Font of Agonies

Enchantment

Whenever you pay life, put that many blood counters on Font of Agonies.
, Remove four blood counters from Font of Agonies: Destroy target creature.

2019-01-25:
The 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.
2019-01-25:
An 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.