Complex sentence: The unicorn was also later featured in the "Dungeons & Dragons Rules Cyclopedia" (1991), and the "Dungeons & Dragons Adventure Game" set (1999).
Split into simpler sentences: The unicorn was also later featured in the "Dungeons & Dragons Rules Cyclopedia" (1991), Various. TSR, 1991 and the "Dungeons & Dragons Adventure Game" set (1999).