No, you cannot do this either; you hit the same issue as all the other cases. Many examples require the two formations to be within a specified distance, "within 15 cms of the Farseer" in this case. Where the Farseer is in the webway, you cannot 'measure' to his exact location - and before you ask, NO, you cannot measure to a 'gate either (the webway is effectively in a different dimension to the battlefield).
To re-itterate,
any "ability" that is off-table cannot be used to influence something that is on the battlefield. Indeed in principle, there is *no* interaction between on-table and off-table formations.
The
ONLY exception to this is the Supreme Commander - once he is actually on the battlefield, you may use his re-roll for an off-table formation that failed its activation test or it's rally test.
Note that here you are actually asking two questions, both of which are not permitted
- At the start of the turn, the Farseer in the webway may not be used to summon the Avatar onto the battlefield - the Avatar cannot be placed within 15 cm of the Farseer.
- Once he has been summoned, the Avatar cannot use "commander" to control formations in the webway - the formation in the webway must have a "unit within 5cm of a unit from the commander's formation", and you still cannot measure into the webway.
