Junglers are going to be seeing a lot of the new Standard set in Season 4. Now that they can start with both Bumba's Mask and another Starter Item, Ratatoskr and Serqet both have incredible clear rates, powerful gank potential, awesome mobility, hard crowd control, and fantastic damage in both sustained and burst varieties.
Everything you want out of an Assassin (and most Junglers), these two have in spades. Successful Conquest grinders in Season 4 are going to need to know how to play both with and against this deadly duo -- and Junglers would be wise to learn how to pilot them.
Ratatoskr is a Jungle Assassin's fuzzy dream -- he has no real weak phases, can escape from very nearly anyone, has a semiglobal Ultimate in Through the Cosmos, and even has sustain attached to his Boots.
Ratatoskr excels in very nearly every aspect of Jungling a majority of the time. And while some gods or goddesses may have his number in certain phases of the game, very few can match this dirty Rat across all of them.
But he really shines in the hands of a pilot that understands exactly when to use which awesome aspect of Sly Messenger. When to use his Ultimate as an escape, as an engage, or even merely as an information gathering tool can make or break Ratatoskr players, as can picking and choosing whether to abuse his mobility and crowd control to take out high-value targets, or to escape fights that seem nuts to battle out.
The Goddess of Venom and one of the standout Junglers of Season 2 is back. While her clear left a little to be desired for much of Season 3, having both Bumba's and Bluestone Pendant at game start -- plus a helpful roaming support to take aggro -- puts Serqet back on top.
This combo makes Serqet's early game pretty incredible, as Bluestone Pendant and Deathbane together will almost immediately destroy any Jungle camp. That means this fearsome Serq du Soleil is free to frolic all over the enemy's backline and high-priority targets.
Deadly, mobile, and with very few exploitable weaknesses, Ratatoskr and Serqet are the two Junglers poised to burn the brightest in the dark of early Season 4. Together, they are the new standard, but I wouldn't worry about taking a good long look. You'll be seeing plenty of them soon.