Hi, can anyone tell me, does the greyseer's lair count as the first skaven card played in the turn for triggering its effect (eg: i play greyseer's lair and then have to wait until next turn or can I play another skaven card this turn and lower its cost?)

Thanks

Pretty sure it says "next skaven unit" and its a support not a unit, so it wouldn't apply. But even if that is not the case, no, it does not reduce the cost of itself. You have to declare targets and pay costs before you can take an action (playing the card).

The Greyseer's lair says:

'Lower the cost of the first Skaven Card you play each turn by 1'

So if this card is played first in the round (as its keyword has skaven in it) is it classed as the first skaven card played or can I reduce the cost of the next skaven card I play in this round?

I really need a ruling on this asap as I'm trying to run a tournement thanks.

Seems I didn't remember the text quite right, but like I said, you have to pay costs and choose targets to play the support. It IS the first Skaven card played, but its effect is not yet in play, so it can't reduce its own cost. If it did, then having 2 of them in your hand would reduce the cost of the first Greyseer's Lair to 2. If you do have 2 of them, and you play them both in the same turn (and nothing else) neither of them would get the reduction, if you play them on 2 separate turns, then the 2nd one would only cost 3.

Greyseer's Lair does count as the first Skaven card played so it has no effect on the turn you play it. It can't reduce its own cost, and any subsequent Skaven card you play that turn wouldn't be the first.