Sacred Seal
Sacred Seals can be equipped to skill slot S, and are effectively movable Passives.
A Seal can be equipped to one hero at a time, and you cannot own more than one of the same Sacred Seal. Any duplicate seals will automatically be exchanged for 300 Hero Feathers 
.
As a general rule, equipping a Seal at the same time as having the corresponding passive skill equipped makes the effects stack, for example having both the 
Breath of Life 1 seal and the C passive equipped effectively stacks the healing properties of both skills.
Sacred Seals can be earned by completing Quests, clearing Squad Assault challenges and by earning a high score in Tempest Trials. They can also be created and enhanced via the Sacred Seal Forge by using Sacred Coins.