Oh good, I was worried that the current generation of Sentai writers weren't doing enough drugs
Senden 宣伝 【せんでん】 (n,vs) propaganda, publicity, (P)
Just in case the episode doesn't beat the word into you already. By the way, the den is the same as in densetsu/legend (伝説 ) or gaiden/side story. (Ninja Gaiden 忍者外伝)