Fate/Zero, Re:Creators Recommendations
Both anime pull legendary heroes (Fate takes those from world history and lore while Re:Creaters takes those from otaku media) from other worlds into one and seemingly duke it out with each other.
Heroes from legend are brought into modern day and meet up. Fate is a large series with many heroes looking back at their legends, Zero is the better part to be animated so far. Re Creators takes some fictional characters it made up and has them meet their creators and meet other genres.
Both have a dark plot but in fate zero they summon heroic spirits called servants and in Re:Creators anime character are summoned
Both of these series have the same director and they are both anime where powerful figures appear in the real world and fight each other. Fate Zero involves historical figures fighting for the Holy Grail while Re:Creators involves characters from various forms of popular media (anime/light novels/video games) fighting over the fate of the consumer world and the people who created them.