The sabre-toothed cat is a monster added in SLASH'EM. Gived that they only move at speed 12, they're not normally a threat to a careful player who is unburdened and/or fast or very fast. However, they are significantly tougher than other fs you are likely to encounter, doing twice the damage of a tiger and having twice the hit points. A player who is not sufficiently prepared to engage one in melee may end up facing a YASD before he knows what is going on.
These are the well known prehistoric felines with the huge canines. They are also erroneously called saber-toothed tigers.