[quote=@NightmareInd]
<Snipped quote by Ammokkx>

Basicly a combination of:

<Snipped quote by Ryougu>

and:

<Snipped quote by Raddum>

However, I purposely didn't the use 'negated', as that would suggest an effect is activated. Even passive effects of some cards will not work, like 'this monster can not be normal summoned', meaning they now can be tribute summoned but without their original effect. 

On the other hand, since English is not my native language, if you guys know a better way to describe it, feel free to tell me.
[/quote]

That... flat out doesn't work. It's not a mechanic and would cause a ruling headache. Also it'd be broken, as you can now tribute 2, summon Horakthy and win the game (Win conditions are not effects and can not be stopped.)

I mean, if you really want me to give a shot at wording it:

Negate the activation and effect of all Level 5 or higher monsters. Both players can Normal or Special Summon Level 5 or higher monsters ignoring summoning conditions. Level 5 or higher monsters can not be Special Summoned via their own effect.

...but again, in both instances, you'd still get the 'Tribute summon Horakthy, win' situation.