Eternal Winter is the third map of the second episode, Enter Flonne, in Disgaea: Hour of Darkness.
Story[]
Flonne comments on the persistence of Laharl and Etna, and tries to put a sleep spell on them. Etna tries to fast a Fire spell on Etna, and Flonne uses a reflect spell, which causes the fire to hit Laharl.
Strategy[]
There are two 1x3 rows of Zombies, how convenient. Sword users almost assuredly have Blade Rush by now, and spellcasters probably have a 1x3 pattern too.
The Winged have a pretty impressive aggro range, and their Hell Pepper (speaking of 'convenient 1x3s') does pretty hefty damage if the characters aren't over-leveled. Remember that ganging up on enemies is good; one dead enemy always beats several half-dead-but-still-alive ones. Healers shouldn't get too far forward; they probably don't have Espoir yet, so their heals will be very needed.