I need a base, not only because it's fun to have but as miauw62 said because it allow me to gather the useful items that are waiting on the floor of the whole dungeon back into a single location for easy access instead of having to navigate the whole thing if i decide to change my equipment in order to attack a specific branch requiring different set of resistances.
So certainly it's not that needed anymore, but still a very lot more convenient than having to move all other the dungeons/branches to change your equipment.
In other news, i ran into Mennas on Vaults:4 , i had to take the risk to fight him because i wanted a completely clean Vaults:4 to avoid any bad surprise when i'll had to retreat from the nasty Vaults:5 (and trying to lead him to Vaults:3 through stairs would be too much letting him strike me).
And keeping Mennas alive if i need to retreat is a bad idea, as you don't want to deal with him if you're not fully prepared.
Battle started, my servitor + tons of shadow creatures (and not weak ones as we're on Vaults ) fought the damn thing while i was moving a bit away to be able to cast more once i got mana back without having to deal with the silence area.
Unfortunately that huge numerical advantage proved to be nothing in front of Mennas that finally managed to kill the last of my legion with only half of his health gone while i was still too low on mana to even stand a chance (+ him moving to me would have silenced me anyways).
Wasted a potion of haste to run away as far as i could and rest.
Then i went back for round 2 while Mennas was back to full health.
This time the battle went better, Mennas seemed to start getting in big difficulty, i decided to wait at the corner of the screen to still seem him (so the summon nerf "can't attack what the player can"t see" wouldn't kill my army) and instead of launching more meath shield in hopeless fight (as even if he was in difficulty, Mennas was killing fast everything i launched), i kept my mana.
And when i judged there was too few of my troops left, i started to hammer Mennas from far with my Mystic Blast.
To my surprise it worked great, looks like the damage roll for once wasn't too much influenced by my bad luck and it actually wounded the enemy badly until
Decided to leave Mennas sword behind as a warning to anyone foolish enough to attack me (yeah i know Crawl isn't about roleplay and story, but still fun to do, like having a base
)