Oona's Gatewarden

Flying is an evasion ability.

A creature with flying can’t be blocked except by creatures with flying and/or reach. A creature with flying can block a creature with or without flying. (See rule 509, “Declare Blockers Step,” and rule 702.17, “Reach.”)

Multiple instances of flying on the same creature are redundant.

Defender is a static ability.

A creature with defender can’t attack.

Multiple instances of defender on the same creature are redundant.

Wither is a static ability. Damage dealt to a creature by a source with wither isn’t marked on that creature. Rather, it causes that source’s controller to put that many -1/-1 counters on that creature. See rule 120.3.

If an object changes zones before an effect causes it to deal damage, its last known information is used to determine whether it had wither.

The wither rules function no matter what zone an object with wither deals damage from.

Multiple instances of wither on the same object are redundant.