The general idea was to use the Knights and all 3 God cards like Yami Yugi/Atem did in the Final Duel in the Anime. That is why Obelisk got thrown in here, he doesn't really synergize with anything in here, and could very well be replaced by another God or any other card.
Slifer, Ra and Ra Sphere Mode are searchable by Thunderspeed Summon. Obelisk can also be summoned by Thunderspeed Summon tho, just not be searched by it.
Summoning Isolde is very easy. Use her first effect to search Infernoble Knight Renaud, and her second effect to discard an Equip Spell from your Deck to special summon Fire Flint Lady right from your deck. This allows you to special summon Renaud from your hand, and it lets you recycle the Equip Spell you just discarded. Now you have 3 monster (and an Equip Spell of your choice) which can be tributed for a god or linked away.
Magnum Shield allows even your normal monsters to become quite the beat sticks. I even used it on Idaten the Conqueror Star and Arcana Knight Joker. But there are a lot of options for Equip Spells, so choose whatever you want.
If Ra is summoned using Ancient Chant and the three Knights as tribute fother, Ra will start out with a whopping 5000 Atk.
Be aware that the recycle effect of all the Poker cards can also be activate be returning a Warrior Extra Deck monster back to the Extra Deck. This allows you to easily summon multiple Isolde and Arcana Extra joker per duel.