The role of Sinister Heavy Fermions in Glashow’s SU(3) × SU(2) × SU(2)′ × U(1) model is to offer in a unique frame relic helium-like products (an ingenious candidate to the dark matter puzzle), a solution to the See-Saw mechanism for light neutrino masses as well as to the strong CP violation problem in QCD. The Sinister model requires three additional families of leptons and quarks, but only the lightest of them, the heavy U-quark and E-electron, are stable. Apparently the final neutral heliumlike (UUUEE) state is an ideal evanescent dark-matter candidate. However, it is reached by multi-body interactions in the early Universe along a tail of more manifest secondary frozen blocks. They should be now here polluting the surrounding matter. Moreover, in opposition to effective $$U\bar U$$ pair annihilation, there is no such an early or late tera-lepton pairs suppression because: (a) electromagnetic interactions are weaker than nuclear ones and (b) the primordial helium nucleus (4He)++ is able to attract and capture (in the first three minutes) E − fixing it into a hybrid tera-helium ion trap. This leads to a pile up of (4HeE −)+ traces, a lethal compound for any Sinister Universe. This capture leaves no tera-lepton frozen in (Ep) relic, otherwise an ideal catalyzer to achieve effective late E + E − annihilations, possibly saving the model. The (4HeE −)+ Coulomb screening is also avoiding the synthesis of the desired (UUUEE) hidden dark matter gas. The (4HeE −)+ E − behave chemically like an anomalous hydrogen isotope. Also terapositronium relics (e − E +) are over-abundant, and they behave like an anomalous hydrogen atom: these gases do not fit by many orders of magnitude the known severe bounds on hydrogen anomalous isotope, making shadows hanging over a Sinister Universe. However a surprising and resolver role for Tera-Pions in UHECR astrophysics has been revealed.