The abyss rite lets you choose an experienced mercenary to attempt abyssal awakening. A candidate needs 10 abyss battles and a victory alongside the party over an abyss floor boss, then pays shards to face their shadow and its companions without allies.
Open "Abyss Rite" from "Base" to see each candidate’s requirements and shard cost. Select a mercenary to compare their current state with the branded state before starting the rite.
Consider the loss of their former racial synergy before choosing to turn a mercenary abyssal. Victory grants awakening on return; defeat refunds the shards and causes an injury lasting 2 weeks.
The base limit is 3 branded mercenaries, and the rite costs more as their number grows. Read the warning before using a perk to expand that limit, since erosion can drain awakened mercenaries’ morale and will.