The Oblivion Catalyst is an item added in AbyssalCraft, mainly used as a power source for certain things. It is essential to progression, as the Gateway Key requires one.
In crafting table (prior to AbyssalCraft 1.8.8 Beta)
SO = Shard of Oblivion
RD = Redstone Dust
EE = Eye of Ender
Infusion Ritual (post AbyssalCraft 1.8.8 Beta)
Infuse an Eye of Ender with 4 Shards of Oblivion and 4 units of Redstone Dust. Requires 5000 PE (as of AbyssalCraft 1.9.12)
A sacrifice is required to complete this ritual.