RD Playguide: Endgame 1
Prep:
This map has the greatest density of Generals (out of two in which they are present). So, bring Thani and your Hammers. After this map, you won't need them.
It also has the greatest density of Sages and is the only tower map with status staves (although the bosses can still cause statuses), so Pure Waters, Ward, and Restore are all quite useful. Obviously, staves to your healers, items to low-Res units.
Start making complete loadouts. Chip weapons are no longer necessary; you've accumulated your elites. But you may want, at least temporarily:
The strongest available weapon for your units (either an SS weapon or a forged one)
Slightly weaker weapons with more uses, to ensure that your high level ones don't break too soon
Weapons with effective bonuses or added effects (Brave or unique ones, mostly). Horseslayers, however, are redundant.
Additional weapons of each type that your unit is able to carry
At least one ranged weapon for each unit, of the highest level available
Healing items, potentially several different ones if you have room
Laguz only - Gems, Stones, and Olivi Grass. If you didn't bring non-royals, your two Gems can go to Kurth and Reyson (Ena can take a Stone and be fine, since Dragons lose gauge so slowly).
Boss Type(s): Lekain is a coward who Rewarps away as you approach, but occasionally Rewarps back later (why, I don't know). Best to catch him after a Rewarp, so he can't retaliate, because Corona is an annoying skill to deal with. Hetzel is stationary and can't even damage you, but is a major threat so long as he can Sleep and Silence you.
Map Tips:
Check out the terrain. There are 3x3 squares of Wardwood in the center, and this is important. There are two major status threats (Hetzel in the NE corner and a Bishop on the northern edge), and Wardwood is the easiest way to limit the likelihood of being affected by them.
The Double Bow is in the hands of a Sniper on the "ledge" on the west side. He's easiest to take out with a Brave weapon via a flier.
Lekain has an area attack that silences virtually everyone (Kurth was safe this time, but I'm not actually sure why). This happens at the end of the third turn, so put Restore on your healers if possible. Even better, try to put your magic units beside Ena.
Reinforcements appear in large groups in the northern and southern extremes of the center of the map. These are primarily Generals in the north, and Bishops in the south. The Bishops are freexp for Micaiah, Sanaki, Kurth, and Ena, whichever of those you so choose. Kurth and Ena have the added benefit of being able to stand in the Wardwood spaces without allowing the Bishops to reap defensive benefits.
Smaller parties to the wings. I managed the west flank with three (Neph, Gatrie, and Sanaki) and the east one with two (Edward and Nolan).
The siege tome Sages need to be taken care of as soon as it can be done safely, to protect units with effective weaknesses to them (fliers and dragons) and those who may be unfortunately put to sleep.