First seen in Mirrodin, Solemn Simulacrum is an invitational card based on a designed submitted by Jens Thorén. It was recently reprinted in the Magic 2012 Core Set. It has two different triggered abilities: one that triggers when it enters the battlefield, and one that triggers when it dies. In most cases, it will enter the battlefield and its controller will search for a basic land, then later when it dies that player will draw a card. However, under some circumstances, the Simulacrum can come and go so quickly that how these triggers work can get confusing.
Let’s assume that a player controls two copies of Heartless Summoning and casts a Solemn Simulacrum. Doing so means two things: this spell didn’t cost anything, and ‘Jens’ will enter the battlefield as a 0/0. Here’s how that all works. When the spell resolves, the Simulacrum will enter the battlefield. This will cause its “enters the battlefield” ability to trigger.
However, before this trigger goes on the stack, state-based actions are checked. Because the Solemn has a toughness of zero, it will go to the graveyard. This will cause its “dies” ability to trigger.
At this point, we now have two triggered abilities that are waiting to go on the stack. The controller of these two abilities can put them on the stack in whichever order he or she chooses. It does not matter that, technically speaking, the enters the battlefield ability triggered first. The controller can put this one on the stack second if he or she wishes. These abilities will then resolve in LIFO (Last In, First Out) order, meaning that the ability that is put on the stack last (i.e., on top) will resolve first.
There are a couple of different principles in the Magic rules that are working here. The first is that state-based actions are checked when a player would receive priority. In other words, they are checked before a player actually does receive priority. Another rule at play here is that when a player does receive priority, triggered abilities that are waiting to go on the stack will go on at that time before they can play anything. Finally, when multiple triggered abilities are waiting to go on the stack, they are placed in APNAP order. This means that those controlled by the active player go on first, followed by those controlled by the non-active player. As mentioned above, the order that these abilities controlled by one player triggered does not determine the order that they are put on the stack. The deciding factor is the choice of their controller.