PS1!Seiken Densetsu and Final Fantasy Tactics aren't really connected.
In my FFT save file, I got all the secret characters (including the monster ally in the Deep Dungeon), including Cloud, and even went through the trouble of getting his sucky Materia Blade, because he needs it to perform Limit Breaks. >_>;;
How to get to the deep dungeon thingie?I'm still trying to get the secret characters.And most of the time in Tactics My pet Entei(Red Cougar)most of the time saves my life.And does a big damage sometimes 200 over....He is still lvl 38....While in Legend of Mana he um...helps...a bit...>.>!Im still trying to finish Legend of Mana as well....Although it hangs when you beat the mana tree,but the chars are movin'.>.>
You will need to be near the end of the game, the safest earliest time is after defeating both Dycedarg and Zalbag, and it might be better for you if you beat Dycedarg's Lucavi form as well. Afterwards, go to Warjilis Trade City and you should hopefully see a conversation take place. Then the path to Deep Dungeon should open. You can get Byblos there.
Deep Dungeon Tips -
Use Movement Ability MOVE-ITEM FIND in order to get the items in the Deep Dungeon. It's also very safe for you if you're level 99, though if the enemies level is determined by your average team level, they will also be level 99.
Use Teleport movement skill to see the entire map... And when you get to the bottom-most floor, if you're not strong, you'll die to Elidibs' Zodiac Summon, which you can learn if a Summoner gets hit by it and survives.
.Ohh....And did you notice in Legend of Mana wherein after you defeat the lord of Jewlels 1000 in Bejeweled City your char will cry then turn to stone?Then every Jumi will be alive and cry then you will be alive again?Its like in Pokemon the 1st movie!Only that Ash didnt cry to turn into stone but still its very the same....Imagine that....