Togami Explains: Arena Trap

I find myself explaining this a lot, so I figured I’d write a guide about it.

Starting in Pokemon Emerald, many abilities got external field effects if your party lead has them. This applies even if said party lead is fainted. A common example is Flame Body, which you use to hatch eggs. Arena Trap does the same thing when it comes to encounter rates—it doubles that. While facing even more Zubats is a bothersome prospect, this is extremely useful if you time it right.
From spreading Pokerus to Friend Safari shiny hunts, there are cases where you’d benefit from more random encounters. By combining Arena Trap with Encounter O-Power level 3, you quadruple your encounter rate. This is extremely efficient; if you are going to seek that shiny, why not get more chances of running into one per sitting?

In the older games, this is also useful. In gen 3-4. Because you cannot use the White Flute for an extra 1.5 times encounter rate (Triple with Arena Trap), it is pivotal to use Arena Trap in Pal Park to expedite the process. This also applies for time sensitive situations, such as the Bug-Catching Contest, and even the Safari Zone.

Illuminate has the exact same effect as Arena Trap. If you prefer to have a Starmie lead over a Dugtrio, go for it.

TL;DR use Encounter O-Power more, have an Arena Trapper with you during Friend Safari shiny hunts