Urshifu, on the other hand, is only used in the late game, so were fine with a thinner line
[5] The classic example is something like, If I let you resolve your commander will you agree to not counter mine next turn? Basically, both of you get something out of it
If you choose the second mode and the creature you don't control is not a legal target as Archdruid's Charm resolves, you'll still put a +1/+1 counter on your creature
I would respond by Thoughtseize on Elixir of Immortality, and then we end up in a situation similar to the play Warden first situation described above...except my opponent gets one less attack in
Faces of the Past, Moraug, Fury of Akoum, Jeskai Ascendancy and Intruder Alarm are prime candidates