i saw this over on dakka regarding the wording around summoned bloodthirsters...thoughts?
Bloodthirsters are summoned via Blood Tithe at the beginning of your turn. It doesn't say Movement Phase, it says Your Turn which is a very different thing from Movement Phase. Normal Deep Striking units happen at the start of the Movement Phase. Bloodthirsters are summoned before the start of your Movement Phase.
In the Movement Phase during which they arrive, Deep Striking units may not move any further, other than to disembark from a Deep Striking Transport vehicle if they are in one.
Did the Bloodthirster arrive in the Movement Phase?
No. It explicitly says it arrives before the Movement Phase.
Therefore the Deep Strike quote above is irrelevant to the issue, as it only applies to those units that arrive in the Movement Phase.
In fact, the quote only says that those that arrived in the Movement Phase cannot move any further. So the summoned Bloodthirster can not only change flight modes, but can also move normally. However they cannot charge still.
Sequence of events:
1) Bloodthirster is summoned at the Start of Your Turn and is counted at Swooping.
2) Movement Phase begins. You must declare the flight mode as the rules tell you. You can choose to change flight modes now.
That simple. The rule says nothing about Reserves, and the inclusion of the Movement Phase specifically in the Deep Strike rule makes it largely irrelevant to the Bloodthirster summoning.