Alright, wording is a bit confusing, but I got you. Let's see here:
Spirit of Heroes
Equip Spell Card
Activate this card by paying 2000 LP, then target 1 monster in your GY: Special Summon that target and equip this card to the targeted monster. You cannot Special Summon other monsters with this effect with the same name as the targeted monster this Duel. If the equipped monster leaves the field, or if this card leaves the field: Banish both this card and the equipped monster face-down. The ATK and DEF of the equipped monster are each 500 points lower than the highest face-up monster's ATK on the field. The equipped monster is unaffected by card effects, except for those activated as Chain Link 2 through 5 during the Battle Phase that affect both the equipped monster and the monster your opponent controls with the highest ATK. You can only activate 1 "Spirit of Heroes" per turn.
Now, what kind of strategy did you have when you made this card? The monster's immunity to card effects is very restrictive, and is almost immune to any kind of Spell or Trap or monster effect that your opponent throws out at you. However, considering how the Equip Spell Card takes the monster down with it, the monster really shouldn't be too hard to handle. However, considering how easy it would be then to remove the effect-immune monster if so, I'll just suppose that you also meant for the Equip Spell Card to be immune as well.
Concerning the ATK and DEF of this card, it shouldn't be too hard to remove this card from the field, considering how its stats are always dependent on your opponent's monster with the highest ATK. You can always take advantage of your opponent's hitters and attack his/her weaker cards, but when it is his/her turn, you must have a good defense for your monster; if that one monster dies the turn after you had activated the card, you'll have lost 2000 LP and a good monster with really good effect-immunity.
Now, this card might work. The effect-immunity and its easy usage is pretty nice, and always having -500 on the field will restrict it from completely destroying your opponent. You just have to make sure that you keep the monster safe during your turn, and if I were you, I would just make the Equip Spell Card immune as well. Thank you for reading.