Sjoring Hard-Heart Vivec Fighter's Guild Quests
Sjoring Hard-Heart is the current leader of the Fighter's Guild in Vvardenfell and one of the two quest givers in Vivec for this guild. Once you become the rank of Master (9) in the Fighter's Guild you'll have access to the quests from Sjoring Hard-Heart; completion of his final quest will result in you becoming the leader of the Fighter's Guild.
If you talk to Percius Mercius about Sjoring Hard-Heart he'll tell you that he is actually corrupt and has been bought by the Camonna Tong. Percius Mercius will ask you to kill Sjoring Hard-Heart as his final quest and assume his role as leader of the Fighter's Guild. Which path you choose is entirely up to you.