Krishna Chaturdashi is the name for the 29th Tithi (lunar day). It's the 14th Tithi of Krishnapaksha. It's nature is Ugra Prada, which can be interpreted as "increase of aggression and aggressiveness". It's good for following works: bad works, attack by deception, hunting, poisoning, war, weapon, making of (fire) arms, fire, arresting; success in cruel works, steel. As it is Galagraha Tithi, it should be left in all Manglik works. Also it's bad for travelling & hair cutting.
Shiva is Devata which rules Chaturdashi (referring to Muhurta Chintamani and Poorva Kalamrita), who's the last deity of great Hindu Triad (Brahma, Vishnu, Shiva) holding a power of destruction. Everything that relates to destruction, death, overcoming any obstacles or limitations, Moksha (spiritual liberation) is good for this Tithi and no creative work should be done during it. As per Brihat Samhita and Purva Kalamrita classical texts, Krishna Chaturdashi is ruled by Kali that also shows Chaturdashi's destructive nature. Kali, translated as "She who destroys", also known as Kalika, is the Hindu goddess associated with eternal energy. The name Kali means "the black one" and comes from kāla, which means black, time, death and relates to Shiva, lord of death and transformation. Kali is represented as the consort of Lord Shiva, on whose body she is often seen standing. Since Shiva is called Kāla or Mahakāla - the eternal time, thus, Kali, his consort, also means "the Time" or "Death" and is considered the goddess of time and change of the state because of Moksha. Various Shakta Hindu cosmologies, as well as Shakta Tantric beliefs, worship her as the ultimate reality or Brahman. She is also revered as Bhavatarini (literally "redeemer of the universe"). Comparatively recent devotional movements largely conceive Kali as a benevolent mother goddess. She is associated with many other Hindu goddesses like Durga, Bhadrakali, Sati, Rudrani, Parvati and Chamunda. She is the foremost among the Dasa Mahavidyas, ten fierce Tantric goddesses. Thus all spiritual activity or just bad activity that moves to Moksha and destruction of Maya (illusion) as well as moving Ahamkara (ego) towards God is very good during Krishna Chaturdashi.
Being Rikta (that can be translated as "empty hands", "scanty", "destitute") and ruled by Shani (Saturn), the 14th Tithi of Krishnapaksha is suitable for following works: arresting, poisoning, uses of weapon, surgery, igniting fire. Travelling in any direction is strictly prohibited and should be avoided during Krishna Chaturdashi.
During the vedic month Jyeshtha Krishna Chaturdashi becomes Maasa Shunya Tithi, which is considered unauspicious in succeeding in works started during this Tithi. Krishna Chaturdashi is also considered to be Galagraha Tithi which according to classical texts should be left in all Manglik elections.