Self-Forming Clay is activated by cards that cost your HP. Therefore, assuming the block it produces actually gets used, it will effectively negate the disadvantage of paying 3 HP, and can even turn paying 1 or 2 HP to your advantage. For example, Brutality or Combust will cause you to gain 3 block a turn. However, note that having multiple of the same power that does this (for example, having 2 Combusts) will still only grant 3 block for that turn.
Update History[]
Weekly Patch 51: Recursion
Fixed Self-Forming Clay relic triggering incorrectly off of prevented damage from Buffer power.