Along with Assassin reworks, several new gems are being added in 3.8.0, and now they have been revealed, leaving only the new mine skills to be seen!
First, Cobra Lash allows you to throw a copy of your weapon, similar to Spectral Throw, but it chains through enemies, with added chaos damage, chaos conversion, and a bonus chance to poison. It also gives critical strikes an additional 50% bonus to poison damage multiplier, potentially keeping it quite powerful late in the game.
While Cobra Lash is available at low levels, Pestilent Strike becomes available at a higher level, and applies a debuff in addition to poisoning foes. Any enemies that die with the debuff active explode, creating a damaging area. The damage is based on the total poison damage remaining on the enemy, which is potentially enormously powerful. Keep in mind that it is, however, a strike skill, meaning that its clearspeed may be limited.
Withering Step applies a new buff called Elusive, increasing your movement speed by up to 40%, and your attack and cast speed by up to 20%. This debuff wears off as you attack, decreasing down to 0%. It can be found through this skill and from the Assassin ascendancy. It also applies withered to all enemies that enter an area around you, once per use.
Finally, Nightblade is a new support gem, exclusive to claws and daggers, similar to Close Combat and Shockwave. It grants base critical strike chance and causes you to gain Elusive on critical strikes. Elusive gained this way adds critical strike multiplier, and this bonus scales with any increased Elusive effect you may have, granting up to 100% critical multiplier by level 20.
You can check out all the new stuff in action in the official video here: