At the end of the Saga of Zath, all characters were kept and moved to Crom regardless of progression. These newly-merged characters were locked by default. If you were level 20+, you also received an additional character slot. You could either use that slot to unlock your Saga character, or use it to unlock another locked character on your account. 
Not all of this information will apply for the Saga of Blood, but you may still find it helpful to review:
Details specific to the end of the Saga of Blood will be released closer to that time, so keep an eye out for updates both here and on our website.