It turns out that there are actually too many powerful cards that use triggered abilities to even name all of the likely suspects here
The latter which I recently made the Top 8 of a Vintage Challenge with on Magic Online, but then an order I made for Modern Dredge arrived, so I decided I needed to write about that instead
US 5662332, Richard Garfield, "Trading Card Game Method Of Play", issued September 2, 1997, assigned to Wizards of the Coast "The Year in Gaming"
When using the Shift 5 ability, which allows the six-cost card to be played one turn early if a cheaper Merlin can be commandeered for the cause, Merlin gets to make use of another feature called Overdeveloped Brain
You can also pair them with cards like Impact Tremors or Warstorm Surge