Hey

The card reads "Choose a Space Marine that has at least 1 Support Token (if able). Discard 1 Support Token from him and 1 Genestealer engaged with him (of your choice)"

If I apply the effect strictly, even if there are no marines engaged with GS, one of the marines MUST lose (=waste) a support token.

However my guess is the card is badly worded and should be "choose a marine with a support token AND engaged with at least one GS… (the rest the same)"

This will fit the intention and theme of the card, and also will balance the fact that the card has a supposedly "benign" effect

What do you think?

I would say that you can play this card however you want without changing the difficulty too much. I have always played that you must discard one support token, even if you aren't able to get rid of a genestealer.

The bigger trouble with reading this card literally is that it says 'discard' a genestealer, instead of slay. Unless we assume it means slay, this bypasses alot of rules. There is not rule against discarding genestealers under the power field, or Brood Lords, Death Leaper, or Elite tyranids with other other genestealers in the swarm. However, since the victory condition on the Brood Lords and Death Leaper is that they must be slain, we also bypass the victory condition.

I just ended up in situation where my last Space Marine was flanked on the left by 2 normal GS and on the right by a Brood Lord.

1) Am I able to discard the Brood Lord as a result of 'For my Battle Brothers'?

2) If I do, and the Brood Lord isn't "slain"… does my game end in a loss?

1) The brood lord is alone, so you can definately discard him whether you consider discard to be the same a slay or not.

2) By a literal reading of the cards, you didn't slay the brood lord and therefor can only win by killing all genestealers and emptying the blip piles. However I recommend reading this event card as though 'discard' meant 'slay', in which case you win immediately.