Context: Yato 夜ト, who is a God fighting spiritual beings related to human's negative feelings, goes to the hospital make a visit to someone, and says:
kon'ya mo shikeru 今夜も時化る Tonight, too, will be stormy.
shikeru - for a sea to be stormy. The series is based on Buddhism, using terms like shigan 此岸, literally "this shore," and higan 彼岸, literally "that shore," refer to "this world (of the living)" and "that world (of the dead)," respectively. Consequently, saying "the sea will be stormy" implies those from that world will come to this world in a more chaotic manner.
(koko) byouin wa yatsurano soukutsu da 病院は奴らの巣窟だ (This place) the hospital is their lair.
koko ここ, "here," "this place" is used as reading for byouin 病院, "hospital," because "here" is "the hospital," that's where the character was when he said that.
{shinki mo inai} ima nagai wa muyou 神器もいない今長居は無用 Now [while] {[I] don't have a regalia}, a long-stay is unnecessary.
shinki 神器, literally "divine instrument," also translated to "regalia" in English, refers weapons to fight spiritual beings. Since these weapons are actually other characters that transform into weapons, and not just objects, the animate existence verbiru 居る was used instead of the inanimate aru 在る.
The temporal nounima 今, "now," is qualified by a relative clause in this sentence.
