Irelia vs Mordekaiser

Mark your targets with Flawless Duet (E) or Vanguard's Edge (R) before Bladesurge (Q): if the target is Unsteady or dies to it, its cooldown resets.

Before a trade, hit minions with Bladesurge (Q) to stack Ionian Fervor (passive): each stack gives attack speed, and at max stacks your autos hit harder.

Place the two blades of Flawless Duet (E) on either side of your target: only enemies caught between them are stunned.

Use Defiant Dance (W) to absorb a burst: you take less damage while charging, and the longer you hold it, the harder the release hits.

Stay near your minions against Obliterate (Q): its damage increases when it hits only one enemy.

Dodge Death's Grasp (E): it pulls you toward him, into his other spells, and it has a 16 to 8 second cooldown.

If you have range, kite him: Mordekaiser has no dash, and only Death's Grasp (E), which pulls you in, closes the distance.

In Realm of Death (R), save your mobility spells to escape him rather than for the duel: he steals part of your stats, and keeps them if he kills you.