Copyright (c) 1977 Invicta

Ergo is played on an empty 9x10 square board:

DROP - A player, on his turn, can drop any stone on an empty cell, or move one of his pieces.
If a piece is dropped unto one of the 34 edge cells, it must a Lion piece; otherwise (the remaining 56 cells which are called the Arena), the piece must be Soldier. 
The maximum number of pieces on the board for each player is 12.
The Soldiers may move to an adjacent (orthogonal) empty cell.
If a Soldier moves to the edge, it is promoted to a Lion.
Lions may move to an adjacent (orthogonal or diagonal) empty cell, if they are not at the edge or if they move from the edge to the Arena.
Lions may also move along the edge as far as they want, even around corners, but they may not jump over other pieces.
There is no capturing.
GOAL - A player wins when he makes a 5 or more in-a-row (orthogonal or diagonal).
The pieces may be located at the edge and consist of both types of stones.
Repetition of the full board position three times results in a drawn game.

The rules are displayed in this webpage (it's in German). I would like to thank Ralf Gering for pointing it out and also for translating the rules to English, from which I based this text.

An example

Green's turn. The Green Lion at j1 can move to cell [1] and wins next turn. Black cannot stop it. Soldiers do not move diagonally.

Some hints (also described by Gering):

1) Try to force your opponent to place more pieces than you. The pieces in your hand are strongest. The player who is able to place the last piece has an advantage.
2) If you block a row of three, do it at the edge (if possible) to get a
3) Lions are strongest at the edge.
4) A broken three (similar to Renju) should always be blocked by putting a
piece in the gap.
5) Balance attack and defense in the opening or you will lose early in the
middle game.
6) The game is more strategic than you think. Build strong positions, such
as Fours, and you will win, even if you don't see how.
7) Control the center and attack from the edge!