From Carl Icahn’s point of view, Illumina Inc.’s desired reintegration of its former spinoff is more a poisoned chalice than a holy Grail. In his opening salvo to a proxy fight, Icahn published an open letter March 13 to other Illumina shareholders referencing the “extreme displeasure” of investors with Illumina’s “reckless” determination to acquire Grail Inc., despite European regulators’ strong opposition to the deal.