Basic Ra Deck

Search guardian slime by crystal girl or ice barrier, use guardian slime to search millennium revelation, sun god unification and ancient chant if you dont have ra, and blaze cannon if you can.

Send phoenix to GY (by rainbow life, millennium revelation if you have it in your hand or by foolish burial) if you can (this will make the combo much stronger and help you protect ra if you cant OTK).

If you dont have guardian slime on the field (destroyed by opp's card or discarded to use rainbow life): Use ancient chant to search ra, activate millennium revelation and discard ra to search monster reborn (if you have phoenix, discard it instead), then:

+ If you still have ra or ra's ball in your hand, use monster reborn to summon guardian slime and use it to summon egyptian god slime, banish ancient chant in GY, tribute egyptian god slime to summon ra and pay LP to increase its ATK (if you summon ra's ball then tribute it and summon ra), set sun god unification and activate it (if you summon ra by ra's ball then use the effect of sun god unification to pay LP to increase ra's ATK), attack opponent with your ra (use blaze cannon if you have). If you cant OTK with your ra, activate sun god unification's second effect and tribute ra, the phoenix will jump up and ready to attack.

+ If you dont have ra in your hand because you discard it to search monster reborn, then activate the second effect of millennium revelation (allow to summon ra via monster reborn, recommend only if you have phoenix in your GY or you can OTK), use monster reborn to resurrect ra, activate sun god unification's effect to pay LP to increase ra's ATK (or use ra's effect to clear the field first and then activate it), attack opponent with your ra (use blaze cannon if you have). If you cant OTK with your ra, activate sun god unification's second effect and tribute ra to gain LP equal to its ATK (you must do this or ra will be send to the GY with all the LP you paid for its ATK during the end phase by the effect of millennium revelation), the phoenix will jump up and ready to attack.

If phoenix still cant OTK, then simply end the turn, activate phoenix's effect and summon ra's ball, wait until your next turn to do the sun god unification and phoenix combo again.