Can I use the ability of sacrifying the slayers to destroy an attacking unit, even if the attacking unit does not attack my battlefield (where the slayers are placed)?

Thanks for a short response!

Yep. Any attacking unit.

That's what I thought, thanks.

Is the damage of the attacking unit still assigned and applied after I have sacrificied a Slayer to destroy the attacker?

Philos said:

It depends upon when you sacrificed your Slayer :

1) if it is before the Combat Damage Assignment step, then either your Slayer damages nor the destroyed unit damages will be assigned (and even less applied, of course).

2) if it is after the Combat Damage Assignment step, then both your Slayer damages (if tey defended) and the destroyed unit damages will be applied. Of course, the damages assigned to either the Slayer or the destroyed unit won't be applied, as the units will no longer be in play (unless you decide to sacrifice the Slayer after the Combat Damage Resolution step).

So, play the combat steps in order, and keep in mind that assigned damage lose track of whom dealt them. This should allow you to resolve those kind of game situations.

I have also a question concerning these Slayers. Because I somewhere read that there will be cards which need the Slayer keyword to be played, I wonder if these slayers have been forgotten. They are only "warriors" an not "slayers" like the Trollslayers, for example. Is there an errata of this card or has this fact been overlooked?

Greets

Most of the traits in the game are not yet used, so its hard to say. There are currently quite a few traits in the game that only exist on 1 or 2 cards, and most traits are not referenced by anything at all. If there was any errata on the trait, it would be in the official FAQ (there is not).