Also(flash) and(ghost) is good on him too but you cant burst the damage as much as with ignite.
MARKS: 9x Greater Mark of Insight
SEALS: 9x Greater Seal of Resilience
GLYPHS: 4x Greater Glyph of Warding
GLYPHS: 5x Greater Glyph of Shielding
QUINTESSENCES: 2x Greater Quintessence of Insight 1x Greater Quintessence of Fortitude

I tried playing 9/21/0 and 0/21/9 masteries for Morde in a lot of games and this is my feedback. The only good thing about going into the entire defense tree is getting Tenacity and Veteran’s Scars for more early survival. My issue is because I’m throwing away 3% running speed, I feel much slower than I should. I know it may sound minimal, but many squishies who play the game such as Ashe try to make sure they top their running speed so no one can catch them. I maybe more tanky, but if I can’t reach my opponents, my role for dealing damage is completely useless. Speed is very critical when playing Mordekaiser. He’s very easy to kite which creates a problem if you’re slow. Good players will kite you and give you a very hard time. Movement Speed is needed.