Solyman is "il Soldano," i.e. "Sultano," the Sultan, the Turkish King. Together with Argantes, he is the main hero in the Muslim army. It is anyway worth noticing that both Solyman and Argantes (one of the sons of the King of Jerusalem, in GC) play a different political role than in Gerusalemme Liberata. Other characters will also receive a different name, like the Christian knight Rinaldo of GL who becomes Riccardo (Richard) in GC. So, Princess Erminia becomes Nicaea, the same name as the city, and in GC she even turns out to be Solyman's daughter - just, for some unexplained reason, they will never meet, even if both have moved to Jerusalem, independently, because of the war.
Solyman is as unbelievably strong as Argantes, but still more violent: a destroyer, a 'butcher,' a war machine, a juggernaut. In Gerusalemme Liberata he appeared suddenly by night, not described, just a deadly shadow like Alien or Predator. In Gerusalemme Conquistata we first 'see' him painted in the representative tent, but the general impression left by him is the same. The more so as, as it has already been mentioned, in GC the battles undergo a
process of 'Vikingalization' after (before!) the manner of Robert E.
Howard. Tasso indeed ennobles him by comparing him not only to the mythical giants but to Hercules --- the whole description is a nearly literal translation from Virgil, Aeneid 7: 666-669.
The fierce side, however, is absolutely not the whole of Solyman. We'll find this out on Monday.