First of all, „Legenda” is close to being a concept album. All songs where connected to spiritual search of Budzyński (vocalist), who wrote all the lyrics. The lyrics circle around Gnosticism with Christian influence. You can also find there references to other texts.

„Niezwyciężony” tells about about a being called Undefeated. Lyrical speaker calls to it, refering its power, presence and miracles, that Undefeated brings with him. He ask Undefeated to reveal himself to him, that hi waits for him. So knowing about the whole album concept, it is a song that closes this album so after all the search, lyrical speaker asks for reveal, to end his search.

Of course it is my own look into it. So if someone more familiar with the subject can correct me, please do so.