Can someones explain me this game mechanic?

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Hallo everybody. Im in Bronze 1 and i got a fight today with something i cant explain to myself.

https://m.splinterlands.io/#/battle/game/process/sl_1ba9262b97aee01d9995aca3ccc0af42

When my unicorn mustang is low on HP it get's healed by something i cant explain.

Can someone help me?

Thank a lot

Can someones explain me this game mechanic? | Ecency