Do any post-RigVedic deities appear in the principal upanishads?

Question

I am taking

Brhadaranyaka Upanishad
Chandogya Upanishad
Taittiriya Upanishad
Aitereya Upanishad
Kausitaki Upanishad
Kena Upanishad
Katha Upanishad
Isha Upanishad
Svetasvatara Upanishad
Mundaka Upanishad
Prashna Upanishad
Maitri Upanishad
Mandukya Upanishad

as principal upanishads.

Are any post-RigVedic deities mentioned in these Upanishads?

By RigVedic, I primarily mean (along with verses dedicated to them)

Indra 250 Agni 200 Soma 123 Aśvins 56 Varuna 46 Maruts 38 Mitra 28[3] Ushas 21 Vayu (Wind) 12 Savitr 11 the Rbhus 11 Pushan 10 the Apris 9 Brhaspati 8 Surya (Sun) 8 Dyáuṣ Pitṛ́ and Pṛthvī Mātṛ́ (Heaven and Earth) 6, plus 5.84 dedicated to Earth alone Apas (Waters) 6 Adityas 6 Vishnu 6 Brahmanaspati 6 Rudra 5

Answer 1

Uma Haimavati appears in the Kena upanishad. She points out to Indra that the yaksha they have seen is brahman and the deva-s won their victory due to brahman.

अथेन्द्रमब्रुवन्मघवन्नेतद्विजानीहि किमेतद्यक्षमिति तथेति तदभ्यद्रवत्तस्मात्तिरोदधे ॥ 3.11॥

स तस्मिन्नेवाकाशे स्त्रियमाजगाम बहुशोभमानामुमाँ हैमवतीं ताँहोवाच किमेतद्यक्षमिति ॥ 3.12 ॥

सा ब्रह्मेति होवाच ब्रह्मणो वा एतद्विजये महीयध्वमिति ततो हैव विदाञ्चकार ब्रह्मेति ॥ 4.1॥

Then the gods said to Indra: "O Maghavan! Find out who this great Spirit is." "Yes," he said and hastened to It. But the Spirit disappeared from him. Then Indra beheld in that very region of the sky a Woman highly adorned. She was Uma, the daughter of the Himalayas. He approached Her and said: "Who is this great Spirit?"

Chapter IV

She replied: "It is, indeed, Brahman. Through the victory of Brahman alone have you attained glory." After that Indra understood that It was Brahman.