mtg blue cards True Revisited Blue Dragon | Adventures in
Description
Except that EDH exists, and it's fairly easy to make an infinite ETB loop with this card around

Leonardo da Vinci Wow, Mr

Considering that around 75% of Standard decks are playing this enchantment, it's becoming a huge barrier of entry for paper Standard

Dimir Guildgate

A single cycle of such spells might not cause a stir, but these moments of power creep seem to happen more and more as WotC has begun designing cards explicitly for use in Commander
