Reclaimation pools are a vital part of a Tyranid invasion. Each invasion goes through identifiable stages. First comes the identification and infiltration of a prey world, when Mycetic Spores land vanguard creatures such as Genestealers and Lictors. These become active, probing defences and assessing the world's ability to resist an attack. Next comes the subjugation phase, when the planet's defenders are assaulted and overwhelmed by swarms of Tyranid creatures. After all major resistance has been overcome, comes the consumption phase as the planet's atmosphere is changed and all genetic material is broken down into reclaimation pools. Creatures such as Rippers and Malanthropes consume all the planet's biological material before jumping into the pools and being consumed themselves. The pools are then harvested by hive ships which enter low orbit and pump the gene-rich biological soup on board via Capillary Towers.