Q:

Who was served his own children cut into pieces?

I'm looking for the name an ancient man who was subject to being served his own children in pieces and eating them unknowingly. He was invited for dinner by the king where this took place.
Later, he had the chance to revenge himself, helping with a battle in which that king was killed.
Does anyone recall who might fit this description? This may have been an actual event but my memory fails me(probably in more ways than this), so I'm putting this into the myths section.
Thanks!
Update: Tantalus may be a candidate for the "king" whereas Demeter for the victim but I am pretty sure in this case it was a father who ate his children and he was later shown the rest of their bodies cut into bieces in baskets.

A:

As I put in comment, this reminded me of Shakespeare's Titus Andronicus play.
In the Wikipedia page, under the Sources section, it cites Ovid's Metamorphoses:

The primary source for the rape and mutilation of Lavinia, as well as
  Titus' subsequent revenge, is Ovid's Metamorphoses (c.AD 8), which is
  featured in the play itself when Lavinia uses it to help explain to
  Titus and Marcus what happened to her during the attack. In the sixth
  book of Metamorphoses, Ovid tells the story of the rape of Philomela,
  daughter of Pandion I, King of Athens. Despite ill omens, Philomela's
  sister, Procne, marries Tereus of Thrace and has a son for him, Itys.
  After five years in Thrace, Procne yearns to see her sister again, so
  she persuades Tereus to travel to Athens and accompany Philomela back
  to Thrace. Tereus does so, but he soon begins to lust after Philomela.
  When she refuses his advances, he drags her into a forest and rapes
  her. He then cuts out her tongue to prevent her from telling anyone of
  the incident and returns to Procne, telling her that Philomela is
  dead. However, Philomela weaves a tapestry, in which she names Tereus
  as her assailant, and has it sent to Procne. The sisters meet in the
  forest and together plot their revenge. They kill Itys and cook his
  body in a pie, which Procne then serves to Tereus. During the meal,
  Philomela reveals herself, showing Itys' head to Tereus and telling
  him what they have done.

So the answer may be Tereus of Thrace, son of Ares, except instead of a final battle you get birds.
From Wikipedia too:

Tereus desired his wife's sister, Philomela. He forced himself upon
  her, then cut her tongue out and held her captive so she could never
  tell anyone. He told his wife that her sister had died. Philomela wove
  letters in a tapestry depicting Tereus's crime and sent it secretly to
  Procne. In revenge, Procne killed Itys and served his flesh in a meal
  to his father Tereus. When Tereus learned what she had done, he tried
  to kill the sisters but all three were changed by the Olympian Gods
  into birds: Tereus became a hoopoe; Procne became the nightingale
  whose song is a song of mourning for the loss of her child; Philomela
  became the swallow, which has no song.

And from Theoi:

TEREUS. A king in Thrake (north of Greece) whose wife and
  sister-in-law slew their infant son and fed him to the king. When he
  discovered their crime, they fled to escape, and sympathetic gods
  transformed them into birds - nightingale and swallow. However, Ares
  (most likely), sympathetic to his son, transformed the king into a
  hawk, so that he could exact his vengeance for eternity on the two
  women.

A:

This sounds like Thyestes, brother of Atreus.  (Atreus was the father of Agamemnon and Menelaus.)

Atreus now sent a herald to lure Thyestes back to Mycenae with the offer of an amnesty and a half-share in the kingdom; but, as soon as Thyestes accepted this, [Atreus] slaughtered Aglaus, Orchomenus, and Callileon, Thyeste's three sons by one of the Naiads, on the very altar of Zeus where thy had taken refuge; and then sought out and killed the infant Pleisthenes the Second, and Tantalus the Second, his twin.  He hacked them all limb from limb, and set chosen morsels of thier flesh, boiled in a cauldron, before Thyestes, to welcome him on his return.  When Thyestes had eaten heartily, Atreus sent in their bloody heads and feet and hands, laid out on another dish, to show [Thyestes] what was now inside his belly.  Thyestes fell back, vomiting, and laid an ineluctable curse upon the seed of Atreus.The Greek Myths, citing Tzetes: Chiliades i.18 ff; Apollodorus: Epitome ii.13; Hyginus: Fabulae 88, 246, and 258; Scholiast on Horace's Art of Poetry; Aeschylus: Agamemnon 1590 ff.

This is the origin of the "Curse of the Atreides". Some family!

A:

After some searching, I found the reference I was looking for:
It was Harpagus, and it was an "actual event" written up by Herodotus. [Source Garden History Reference Encyclopedia]
Wiki, quoting Burkert (Homo Necans) states that:

Herodotus accounts for the turn of Harpagus' support to a version of the cannibal feast of Thyestes.

See: Herodotus, The Histories, 111 ff. and Herodotus: Book One; Early History of Persia (reed.edu) for a guide.

Gee, my memory is still really really sharp when it comes to the details of unfoldings.
Thank you everyone!

