Whenever you sacrifice a permanent, this creature gets +2/+0 until end of turn. , Sacrifice another creature or an enchantment: This creature gains first strike until end of turn.
原文The first ability of Slaughter-Priest of Mogis is a triggered ability, not an activated ability. It doesn't allow you to sacrifice a permanent whenever you want; rather, you need some other way of sacrificing permanents, such as its second ability.
2020/01/24
原文Multiple instances of first strike on the same creature are redundant.