in early you have to play carefull, because you will lose against most heros, but with your passiv it shouldn't be a problem. at lvl3 you can start to poke him down. just use your q, move to him, use w, do some hits and escape with e. Now it's time to use your passiv. you can do this again, and again, and again, and again :p

with lvl 13 muradin gets much stronger. You will be able to beat most enemies 1vs1. hit your enemy with q, if there is no minion very close to him, than jump with your e in his way and use your w. now hit him. with lvl 16 it will do good damage. most time your enemy will survive this with low life, dont case to far, but a bit. you are able to escape most time. just slow with your w and wait for the 1st enemy jumping to you. than stun himand jump with your e over a wall.

at lvl 20 use your spells fast if the first stun is over do the same again. assasins will be dead. At teamfights use e(jump close to the assasins -> q(hit 2 heros, if possible assasins) -> w(hit as many as you can) -> use 1 -> stun 2 enemies again. jump and try to block the enemy way to escape. your w will do much damage against a single target, so a assasin cant escape(if you hitted him before)