[Help] Mobs from higher season to lower season

[WIZARDMASTER]

How to run S13 mobs (from Deep Dungeon,Swamp of Darkness etc.) on S12-1 server ?
What modification are needed ?
We can run new maps on lower season servers but how to import new mobs ?
In server we can add new mobs indexes and spawns, but what and where to change on client ?

Thanks anyway

[MentaL]