well, you really need to see some aspects, you must think about something creative and that makes some sense about the lore overall…
if the elven kingdom is raided, we need to see two things
how the elf survived,
where he is right now, what happened to him?
or
did the elf just ran away inside the forest and after some time fighthing and training himself, then he returned and came up to get revenge
about the ‘‘many centuries ago’’, this is pure lore that you need to write it down, so you
re-check your lore and you can adjust if something is off, matching the current situation
where the elf ( the player) will begin
since the warboss’s soul was sealed, then
Who, who started raiding the elven kingdom? did some orc lieteunant gave himself control and now is leading the raid?
there must be someone else
or
alternative-story:
the orcs just started raiding, since elfs attacked them, now they want revenge
about his sister, the player needs to notice this after the kingdom is in peace and fully controled
by elfs ( again )
after some time, idk, vising his old house, he noticed that his sister went missing…
then he just started a (new adventure) now, raiding the orcs again.
but this time, who is controlling the orcs ‘‘could be’’ the new leader OR ( since they recaptured the warboss soul sealed away, they are trying to awaken it, or they already did it
and now the boss is some strong orc boss or whatever it is ( your decision actually )
[Edit 1]
start in a small custcene, where the elf ( player ) is lying on the ground inside a unknown forest
after some time the player can just, control him, waking him up, or someone else?
( like a fairy in zelda games lol)
now this is pure imagination, you will need to focus your attention on:
what to do? first we need to train, before raiding the elven kingdom to re-capture everything
–search for survivors
– build a home or idk ( pure cosmetic and optional )