Enemies throw and drop more grenades.
Catch is a gold skull featured in most Halo games excluding Halo: Combat Evolved Anniversary, and Halo: Spartan Assault. When activated, it prompts enemies to throw grenades more frequently, as well as providing them with other grenade-related benefits.
Right after you exit from the underground highway, you'll come to a large open-air circular area with a handful of Jackal Snipers and some Elites. The quickest way to get safely to the Skull is to get the next checkpoint by jumping into the Warthog and letting the Marine drive you to the next area. Jump out of the Warthog and backtrack to the large room, and clear the area. Or you can get your Warthog from the bridge and just run right through the platforms and the other part until you reach the place where you find the Wraiths attacking the building where the Marines are (but you don't have to fight them) and then go back and the enemies will be gone when you go back. You will see a large semi-circular beam going from one of the main platforms that goes from the ground up to the top of the two towers. Do a Grenade Jump at the bottom of this beam or drive a warthog backwards partially up the beam and use it as a ledge to get up and walk all the way to the top. Jump over to the ledge of the left tower. Walk to the end of the ledge and you will find the Catch Skull. The Sputnik Skull may be helpful if you have trouble Grenade Jumping.
Do not destroy or physically damage the normal Wraith in any way (though the plasma turret operator can be sniped safely) or the skull will disappear.
- At Lakebed A where you fight an Anti-Air Wraith, a handful of Ghosts, and a standard Wraith, you should see a silo-like building (see image). On top of this is the skull. Look for the ramp that leads over to the platform where the normal Wraith is dropped.
There are multiple methods which can be used to get onto the building.
- Grenade jump.
- Drive the Warthog at the foot of the silo and Crouch jump onto it. Make sure that the Warthog is at the Wraith-side of the silo before attempting the crouch-jump.
- Drive the Warthog between the silo and the wall so that it is turned on its side. Jump onto the red wall, then jump onto the silo.
- Park a Ghost below, then jump from it onto the building. Use a grenade jump if necessary.
- Park one Ghost on the Wraith-side, then get another Ghost and park it on top. You should be able to jump on top of the Ghosts and then onto the silo.
- Take a Deployable Cover and use it between the red wall and the building. Move out of the way and you can use the cover as a stepping stone.
- In Co-op, one player can jump onto the other player's head and then onto the building.
- Hijack the Anti-Air Wraith and maneuver it so the back touches the base of the silo where the ground rises slightly, then get out. The only problem is that this will cause an NPC Hornet to fire upon the standard Wraith, and the Wraith may focus its fire on you, so you will need to work a little quickly. The Anti-Air Wraith should remain still while you jump on the back and onto the top of the silo.
In all its appearances, the skull increases the frequency at which enemy AI will throw grenades. Furthermore, in some titles, namely Halo 2 and Halo 3, it does the same for friendly AI. This causes enemies to throw grenades a disproportionately large amount of the time, instead of firing their weapons.
Additionally, in some titles it makes other changes to grenade-related aspects. In Halo 2, it makes enemies consistently drop 2 grenades, no matter what amount they have remaining. A similar effect, though proportional to how many grenades they have remaining, is caused by the skull in Halo 2: Anniversary.
Unlike in other titles, Catch grants enemies in Halo 3 and Halo 3: ODST an unlimited supply of grenades to throw, although they do not drop this supply. Another unique bonus is given by the skull in Halo: Reach; enemies go through the grenade throwing animation faster, as well as more often.