Guard dog reads
While this model is within 3" of its Leader and is not knocked down or stationary, its Leader gains +2 DEF against melee attack rolls and cannot become knocked down
If this model is slammed into its warcaster does the warcaster get knocked down?
No, probably not. Because you resolve the moment first, then the knockdown of the slammed model.
Nope, as it is within 3" at the time of Impact.
It is not knocked down. When a model is slammed, the following things happen in order:
- It is moved the distance that it is slammed.
- It becomes knocked down.
- It suffers a damage roll.
Effectively, during that first step, if the slammed model contacts a model with an equal or smaller base, the contacted model becomes knocked down. This happens immediately and “interrupts” the movement of the slammed model because the slammed model hitting the warcaster is a triggered effect, which is resolved (at the exact moment or immediately) when the trigger condition is met. After the rules attempt to knock down the warcaster (and can’t because it cannot be knocked down), then the slammed model’s movement ends (assuming it isn’t slammed all the way past the warcaster), and then the slammed model is knocked down.