- "After X enters play" and "After you marshal X" reactions share the same timing window, so if one player marshals Littlefinger and the other player has Harrenhal in play, the first player gets the first opportunity to trigger any relevant reactions. If Littlefinger gets killed first, then his ability cannot be triggered because he is no longer in play.
How does this apply to Maester Aemon (Core)? Does Harrenhal effectively kill him when entering or can he kneel to save himself? — DrNovak 1
No. You marshal Maester Aemon, your opponent reacts to that by using Harrenhal to kill him. Maester Aemon, being in play, interrupts the resolution of Harrenhal's ability, and cancels it. — mplain 195
I mean saves himself from the kill, not cancel. Sorry. — mplain 195