5) Demon Wall
Unless your party is around level 40, you cannot defeat the first Demon Wall in the Tomb of Raithwall. There’s a second Demon Wall in the chamber beyond the entrance, however, and that one must be defeated in order to continue.
You can use the Altars of Contemplation along the bridge to either slow down or speed up the Demon Wall’s progress; if the latter happens, run to the next altar ASAP.
Before you enter the Cloister of Flame in the Tomb of Raithwall, learn the Water spell and buy plenty of Handkerchiefs. It’ll prove useful when battling Belias, a high-powered brawler who also knows Firaja, his version of which inflicts the Oil status. Remove the Oil quickly, and use Protect on the party to cut Belias’s melee damage.
Tiamat knows Disablega and absorbs Wind spells, which can be problematic. Aside from those potential issues, this is mostly a straight-up brawl, which will be won or lost by your melee combatants. Be sure to cast a battery of protective spells before entering Tiamat’s lair, the Ore Separation area in the Henne Mines.