Two or more creatures you control must attack the same player in order for Landroval, Horizon Witness's ability to trigger
This could be highlighting certain Planes (such as a cube that uses cards from all sets that take place in Ravinca and/or cards that depict the plane), characters within the game, being a tribute to a specific Standard environment, or be limited to cards with specific printings, such as retro frames and white borders
Unctus + 2 Untappers (Kiora Follower or Vizier of Tumbling Sands) I havent tried this combo yet, but Im excited for it since each of the cards are close to playable on their own in a Nykthos U Devotion build
Meanwhile, The Scarab God slowly drains your opponents the more Zombies you control, while also giving you a cheap way to steal your opponents creatures and turn them into Zombies
This amazing flexibility and the resulting potential for creative gameplay have helped cement storm as one of the games all-time popular archetypes, both in Commander and beyond