There is no separate notion of slasher, every staker is potentially a slasher. Slashing evidence can be included when you make a block. Doing so is rewarded, so

There is no separate notion of slasher, every staker is potentially a slasher. Slashing evidence can be included when you make a block. Doing so is rewarded, so you are economically incentivized to report slashable offenses if you find them. Blocks are validated and "attested" by everyone else. Failing to produce a block that everyone else accepts (edit: everyone else meaning at least 2/3 which is the quorum used) has at best the economic opportunity cost of what you could have earned and missed on and at worst (if someone else reports a slashable offense on your part that is accepted) a slashing penalty plus you get kicked out of the validators. The rest is game theory. Dishonest validators win the game being dishonest if they are over 2/3 of the validator set. Then they can enforce their bad blocks into everyone else. Otherwise they get slashed or suffer other kind of penalties (inactivity leak if they manage to prevent the network from reaching consensus for a while). So if you manage to bribe or buy 2/3 of the staked ETH then you can attack the network. There is of course a very significant economic cost to it. More interestingly at that point you are strongly aligned with the network itself as you represent a huge % of its value so you would be attacking yourself in a way. This is a notable difference with PoW where miners are not necessarily aligned in economic incentives with token-holders or users.