The age and dimension of the observable universe places a direct constraint on the number of active civilizations, via the Drake-Stross equation. The final term 𝐋 in the classical Drake equation (average lifetime of civilizations) invites speculation on further filters. The extended D-S form adds terms 𝐅𝑐¹ and 𝐏𝑖² —which we postulate have values that can be inferred from the size and age of the observable universe—that quantify the risk of respectively development and use of Cosmological Weapons capable of initiating a new inflationary bubble (so-called Big Bang) within the multiversal foam; their product 𝐏𝑒 (the Eschatological Constant) being the likelihood of a reset to cosmological state, our own 13.7Gly observable universe being the result of the nearest-most-recent such detonation. In this paper we
¹ Fraction of civilizations that develops the Cosmological Bomb
² Probability of a civilisation triggering a universe ending/creating exchange of cosmological weapons

