To elaborate, first, let's look at the rule for Ongoing Reserves (p136):
If a unit enters Reserve part way through the game, such as a Flyer leaving the battlefield, this is referred to as entering Ongoing Reserves. Units in Ongoing Reserve always re-enter play at the start of their controlling player's following turn, but otherwise follow the normal rules for Reserves.The interesting part is that they follow the "normal rules for Reserves." The only deployment method mentioned in the Reserves rules (the paragraphs above Ongoing Reserves) is entering from the controlling player's board edge.
Now, let's look at Deep Strike:
In order for a unit to be able to Deep Strike, all models in the unit must have the Deep Strike special rule and the unit must start the game in Reserve (p135). When placing the unit in Reserve, you must tell your opponent that it will be arriving by Deep Strike (sometimes called Deep Strike Reserve)...That seems straightforward enough. Where it becomes complicated is with units that can deep strike and also choose to go into Ongoing Reserve, while not beginning the game in reserve. The best examples of this are Swooping Hawks and Mawlocs, which have rules to allow them to enter Ongoing Reserve, presumably for the express purpose of using their special Deep Strike abilities. These models can begin the game on the board and use Skyleap at any point or Burrow Turn 2 on, to enter Ongoing Reserves.
The first sentence of Deep Strike throws a wrench into this when it says the "unit must start the game in Reserve." This is fairly cut and dry, and seems to partially counter the point of Burrow and Skyleap; these units must begin the game in Deep Strike Reserve since their special rules allow them to enter Ongoing Reserves only and not give any additional permissions to Deep Strike from Ongoing Reserves.
Interestingly, it seems that there are other units that can also deep strike multiple times. Specifically, Flying Monstrous Creatures which begin the game in Deep Strike Reserve can, and arguably must, return to combat airspace via Deep Strike.
A sticky spot for Deep Strike is what happens to units that use a special ability or psychic power to Deep Strike that suffer a Deep Strike mishap and are placed in Ongoing Reserves. Gate of Infinity is one example. GoI gets around the first sentence by saying specifically the unit arrives using the rules for Deep Strike. The issue is, if the unit mishaps and is placed in Ongoing Reserve, they then seem to have no permission to be deployed via Deep Strike in the following turn. The unit didn't likely begin the game in Deep Strike reserve, and doesn't explicitly have the Deep Strike Special rule.
As an example, if Draigo and Grey Knight Terminators do in fact start in Deep Strike Reserve and mishap, they can return to play using Deep Strike. However, if they began the game on the board, or are joined by a model without Deep Strike, they must then walk on from their board edge, since the unit no longer has permission to Deep Strike, as indicated by the first sentence of the Deep Strike special rule.
Finally, formations like Sporefield and Skyblight for Tyranids present some interesting issues when it comes to interaction with Ongoing Reserves and Deep Strike. What makes these formations a gray area is that they are defined by the ability to regenerate destroyed units on a 4+. Specifically:
Each time a Mucolid Spore Cluster or Spore Mine Cluster from this Formation is completely destroyed, roll a D6: on a 4+ you can immediately place a new unit into Ongoing Reserve that is identical in terms of the original number of models, weapons and upgrades to the unit that was just destroyed. (Emphasis added)With these formations, the original unit is not placed into Ongoing Reserve, but a new unit is. Arguably, this new unit should be able to be declared as arriving via Deep Strike (since they have the Deep Strike special rule), regardless of how the original unit was deployed. However, this is far from cut and dry.
So, in conclusion, my findings are as follows:
- Units that can Deep Strike and voluntarily (or otherwise) enter Ongoing Reserve must begin the game in Deep Strike Reserve in order to Deep Strike when arriving from Ongoing Reserves
- Units that suffer a Deep Strike mishap that did not begin the game in Deep Strike Reserve or do not consist entirely of models with the Deep Strike special rule, must arrive from Reserves by walking on the controlling players' board edge.
So what are your takeaways? Did I overlook or miss an interaction of these rules? Did you learn something new? Let me know in the comments below.